using System;
    using System.Collections;
    using System.Collections.Generic;
    using System.Diagnostics;
    using System.IO;
    using System.Linq;
    using System.Numerics;
    using System.Text;
    using Problem = Tmp.Problem;
    namespace Tmp
    {
    	//using GeometryLong;
    	class Problem : IDisposable
    	{
    		bool IsGCJ;
    		int Repeat;
    		Scanner sc;
    		Printer pr;
    		public Problem(bool isGCJ, Scanner scanner, Printer printer)
    		{
    			sc = scanner;
    			pr = printer;
    			IsGCJ = isGCJ;
    			if (isGCJ) Repeat = sc.Get<int>();
    			else Read();
    		}
    		public Problem(bool isGCJ) : this(isGCJ, new Scanner(), new Printer()) { }
    		public Problem(bool isGCJ, Scanner scanner) : this(isGCJ, scanner, new Printer()) { }
    		public Problem(bool isGCJ, Printer printer) : this(isGCJ, new Scanner(), printer) { }
    		public void Solve()
    		{
    			if (IsGCJ) for (var i = 0; i < Repeat; i++) { Read(); pr.Write("Case #" + (i + 1) + ": "); SolveOne(); }
    			else SolveOne();
    		}
    		public void Dispose()
    		{
    			sc.Dispose();
    			pr.Dispose();
    		}
    		public int Size { get { return 1; } }
    		public const long Mod = 1000000007;
    		RandomSFMT rand = Program.rand;
    		long N, S;
    		void Read()
    		{
    			sc.Read(out N);
    			sc.Read(out S);
    		}
    		void SolveOne()
    		{
    			for (var b = 2L; b * b <= N; b++) if (F(b, N) == S) { pr.WriteLine(b); return; }
    			var div = new SortedSet<long>();
    			var d = N - S;
    			if (d > 0)
    			{
    				for (var i = 1L; i * i <= d; i++) if (d % i == 0) { div.Add(i); div.Add(d / i); }
    				foreach (var x in div)
    				{
    					var b = x + 1;
    					if (F(b, N) == S) { pr.WriteLine(b); return; }
    				}
    			}
    			if (F(N + 1, N) == S) { pr.WriteLine(N + 1); return; }
    			pr.WriteLine(-1);
    		}
    		long F(long b, long n)
    		{
    			var s = 0L;
    			while (n > 0) { s += n % b; n /= b; }
    			return s;
    		}
    	}
    }
    class Eq : IEqualityComparer<List<int>>
    {
    	public bool Equals(List<int> x, List<int> y)
    	{
    		if (x == null || y == null) return x == y;
    		if (x.Count != y.Count) return false;
    		for (var i = 0; i < x.Count; i++) if (x[i] != y[i]) return false;
    		return true;
    	}
    	public int GetHashCode(List<int> obj)
    	{
    		var x = obj.Count.GetHashCode();
    		foreach (var i in obj) x ^= i.GetHashCode();
    		return x;
    	}
    }
    /*class MultiSortedSet<T> : IEnumerable<T>, ICollection<T>
    {
    	public IComparer<T> Comparer { get; private set; }
    	private SortedSet<T> keys;
    	private Dictionary<T, int> mult;
    	public int Multiplicity(T item) { return mult[item]; }
    	public int Count { get; private set; }
    	public MultiSortedSet(IComparer<T> comp)
    	{
    		keys = new SortedSet<T>(Comparer = comp);
    		mult = new Dictionary<T, int>();
    	}
    	public MultiSortedSet(Comparison<T> comp) : this(Comparer<T>.Create(comp)) { }
    	public MultiSortedSet() : this(Func.DefaultComparison<T>()) { }
    	public void Add(T item) { Add(item, 1); }
    	private void Add(T item, int num)
    	{
    		Count += num;
    		if (!keys.Contains(item)) { keys.Add(item); mult.Add(item, num); }
    		else mult[item] += num;
    	}
    	public void AddRange(IEnumerable<T> list) { foreach (var x in list) Add(x); }
    	public bool Remove(T item)
    	{
    		if (!keys.Contains(item)) return false;
    		Count--;
    		if (mult[item] == 1) { keys.Remove(item); mult.Remove(item); }
    		else mult[item]--;
    		return true;
    	}
    	public bool Overlaps(IEnumerable<T> other) { return keys.Overlaps(other); }
    	public bool IsSupersetOf(IEnumerable<T> other) { return keys.IsSupersetOf(other); }
    	public bool IsSubsetOf(IEnumerable<T> other) { return keys.IsSubsetOf(other); }
    	public bool IsProperSubsetOf(IEnumerable<T> other) { return keys.IsProperSubsetOf(other); }
    	public bool IsProperSupersetOf(IEnumerable<T> other) { return keys.IsProperSupersetOf(other); }
    	public void ExceptWith(IEnumerable<T> other) { foreach (var x in other) if (Contains(x)) Remove(x); }
    	public void IntersectWith(IEnumerable<T> other)
    	{
    		var next = new MultiSortedSet<T>(Comparer);
    		foreach (var x in other) if (Contains(x) && !next.Contains(x)) next.Add(x, mult[x]);
    		keys = next.keys; mult = next.mult;
    	}
    	public void CopyTo(T[] array) { CopyTo(array, 0); }
    	public void CopyTo(T[] array, int index) { foreach (var item in array) array[index++] = item; }
    	public void CopyTo(T[] array, int index, int count) { var i = 0; foreach (var item in array) { if (i++ >= count) return; array[index++] = item; } }
    	public bool Contains(T item) { return keys.Contains(item); }
    	public void Clear() { keys.Clear(); mult.Clear(); Count = 0; }
    	public IEnumerator<T> Reverse() { foreach (var x in keys.Reverse()) for (var i = 0; i < mult[x]; i++) yield return x; }
    	public IEnumerator<T> GetEnumerator() { foreach (var x in keys) for (var i = 0; i < mult[x]; i++) yield return x; }
    	IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
    	public T Max { get { return keys.Max; } }
    	public T Min { get { return keys.Min; } }
    	public bool IsReadOnly { get { return false; } }
    }*/
    class SkewHeap<T> : IEnumerable<T>
    {
    	class Node : IEnumerable<T>
    	{
    		public Node l, r;
    		public T val;
    		public Node(T x) { l = r = null; val = x; }
    		public IEnumerator<T> GetEnumerator()
    		{
    			if (l != null) foreach (var x in l) yield return x;
    			yield return val;
    			if (r != null) foreach (var x in r) yield return x;
    		}
    		IEnumerator IEnumerable.GetEnumerator() { return (IEnumerator)GetEnumerator(); }
    	}
    	public int Count { get; private set; }
    	Node head;
    	Comparison<T> comp;
    	public bool IsEmpty { get { return head != null; } }
    	public SkewHeap(Comparison<T> c) { comp = c; Count = 0; }
    	public SkewHeap() : this(Func.DefaultComparison<T>()) { }
    	public SkewHeap(IComparer<T> c) : this(Func.ToComparison(c)) { }
    	private SkewHeap(Comparison<T> c, Node h) : this(c) { head = h; }
    	public void Push(T x) { var n = new Node(x); head = Meld(head, n); Count++; }
    	public T Peek() { return head.val; }
    	public T Pop() { var x = head.val; head = Meld(head.l, head.r); Count--; return x; }
    	// a.comp must be equivalent to b.comp
    	// a, b will be destroyed
    	public static SkewHeap<T> Meld(SkewHeap<T> a, SkewHeap<T> b) { return new SkewHeap<T>(a.comp, a.Meld(a.head, b.head)); }
    	public void MeldWith(SkewHeap<T> a) { head = Meld(head, a.head); }
    	Node Meld(Node a, Node b)
    	{
    		if (a == null) return b;
    		else if (b == null) return a;
    		if (comp(a.val, b.val) > 0) Func.Swap(ref a, ref b);
    		a.r = Meld(a.r, b);
    		Func.Swap(ref a.l, ref a.r);
    		return a;
    	}
    	public IEnumerator<T> GetEnumerator() { return head.GetEnumerator(); }
    	IEnumerator IEnumerable.GetEnumerator() { return (IEnumerator)GetEnumerator(); }
    }
    // [0, Size) の整数の集合を表す
    class BITSet : BinaryIndexedTree
    {
    	public BITSet(int size) : base(size) { }
    	public void Add(int item) { Add(item, 1); }
    	public bool Contains(int item) { return Sum(item, item + 1) > 0; }
    	public int Count(int item) { return Sum(item, item + 1); }
    	// 順位 = item が小さい方から何番目か(0-indexed)
    	public int GetRank(int item) { return Sum(0, item); }
    	public void Remove(int item) { Add(item, -1); }
    	public void RemoveAll(int item) { Add(item, -Count(item)); }
    	// 0-indexed で順位が rank のものを求める
    	// ない場合は Size が返る
    	public int GetValue(int rank) { return Func.FirstBinary(0, Size, t => Sum(0, t + 1) >= rank + 1); }
    }
    class RangeBIT
    {
    	public int N { get; private set; }
    	long[,] bit;
    	public RangeBIT(int N) { bit = new long[2, this.N = N + 1]; }
    	public RangeBIT(int[] array) : this(array.Length)
    	{
    		for (var i = 1; i < N; i++) bit[0, i] = array[i - 1];
    		for (var i = 1; i < N - 1; i++) if (i + (i & (-i)) < N) bit[0, i + (i & (-i))] += bit[0, i];
    	}
    	public RangeBIT(long[] array) : this(array.Length)
    	{
    		for (var i = 1; i < N; i++) bit[0, i] = array[i - 1];
    		for (var i = 1; i < N - 1; i++) if (i + (i & (-i)) < N) bit[0, i + (i & (-i))] += bit[0, i];
    	}
    	public void Add(int from, int to, long value)
    	{
    		Add2(0, from + 1, -value * from);
    		Add2(1, from + 1, value);
    		Add2(0, to + 1, value * to);
    		Add2(1, to + 1, -value);
    	}
    	void Add2(int which, int i, long value) { while (i < N) { bit[which, i] += value; i += i & (-i); } }
    	long Sum(int to) { return Sum2(0, to) + Sum2(1, to) * to; }
    	public long Sum(int from, int to) { return Sum(to) - Sum(from); }
    	long Sum2(int which, int i) { var sum = 0L; while (i > 0) { sum += bit[which, i]; i -= i & (-i); } return sum; }
    }
    class RMQ
    {
    	int N2;
    	int[] segtree;
    	public RMQ(int N) : this(new int[N]) { }
    	public RMQ(int[] array)
    	{
    		N2 = 1;
    		while (N2 < array.Length) N2 <<= 1;
    		segtree = new int[2 * N2 - 1];
    		for (var i = 0; i < 2 * N2 - 1; i++) segtree[i] = Func.Inf;
    		for (var i = 0; i < array.Length; i++) segtree[i + N2 - 1] = array[i];
    		for (var i = N2 - 2; i >= 0; i--) segtree[i] = Math.Min(segtree[2 * i + 1], segtree[2 * i + 2]);
    	}
    	public void Update(int index, int value)
    	{
    		index += N2 - 1;
    		segtree[index] = value;
    		while (index > 0)
    		{
    			index = (index - 1) / 2;
    			segtree[index] = Math.Min(segtree[index * 2 + 1], segtree[index * 2 + 2]);
    		}
    	}
    	public int this[int n] { get { return Min(n, n + 1); } set { Update(n, value); } }
    	public int Min(int from, int to) { return Min(from, to, 0, 0, N2); }
    	int Min(int from, int to, int node, int l, int r)
    	{
    		if (to <= l || r <= from) return Func.Inf;
    		else if (from <= l && r <= to) return segtree[node];
    		else return Math.Min(Min(from, to, 2 * node + 1, l, (l + r) >> 1), Min(from, to, 2 * node + 2, (l + r) >> 1, r));
    	}
    }
    class Program
    {
    	public static RandomSFMT rand = new RandomSFMT();
    	public static bool IsJudgeMode = true;
    	public static bool IsGCJMode = false;
    	public static bool IsSolveCreated = true;
    	static void Main()
    	{
    		if (IsJudgeMode)
    			if (IsGCJMode) using (var problem = new Problem(true, new Scanner("C-large-practice.in.txt"), new Printer("output.txt"))) problem.Solve();
    			else using (var problem = new Problem(false, new Printer())) problem.Solve();
    		else
    		{
    			var num = 1;
    			int size = 0;
    			decimal time = 0;
    			for (var tmp = 0; tmp < num; tmp++)
    			{
    				using (var P = IsSolveCreated ? new Problem(false, new Scanner("input.txt"), new Printer()) : new Problem(false))
    				{
    					size = P.Size;
    					time += Func.MeasureTime(() => P.Solve());
    				}
    			}
    			Console.WriteLine("{0}, {1}ms", size, time / num);
    		}
    	}
    }
    class BinaryIndexedTree3D
    {
    	public int X { get; private set; }
    	public int Y { get; private set; }
    	public int Z { get; private set; }
    	int[,,] bit;
    	public BinaryIndexedTree3D(int X, int Y, int Z)
    	{
    		this.X = X; this.Y = Y; this.Z = Z;
    		bit = new int[X + 1, Y + 1, Z + 1];
    	}
    	public BinaryIndexedTree3D(int[,,] array)
    		: this(array.GetLength(0), array.GetLength(1), array.GetLength(2))
    	{
    		for (var x = 0; x < X; x++) for (var y = 0; y < Y; y++) for (var z = 0; z < Z; z++) Add(x, y, z, array[x, y, z]);
    	}
    	public void Add(int x, int y, int z, int value)
    	{
    		for (var i = x + 1; i <= X; i += i & (-i)) for (var j = y + 1; j <= Y; j += j & (-j)) for (var k = z + 1; k <= Z; k += k & (-k)) bit[i, j, k] += value;
    	}
    	public int Sum(int x0, int y0, int z0, int x1, int y1, int z1)
    	{
    		return Sum(x1, y1, z1) - Sum(x0, y1, z1) - Sum(x1, y0, z1) - Sum(x1, y1, z0) + Sum(x1, y0, z0) + Sum(x0, y1, z0) + Sum(x0, y0, z1) - Sum(x0, y0, z0);
    	}
    	int Sum(int x, int y, int z)
    	{
    		var sum = 0;
    		for (var i = x; i > 0; i -= i & (-i)) for (var j = y; j > 0; j -= j & (-j)) for (var k = y; k > 0; k -= k & (-k)) sum += bit[i, j, k];
    		return sum;
    	}
    }
    class BinaryIndexedTree2D
    {
    	public int X { get; private set; }
    	public int Y { get; private set; }
    	int[,] bit;
    	public BinaryIndexedTree2D(int X, int Y)
    	{
    		this.X = X; this.Y = Y;
    		bit = new int[X + 1, Y + 1];
    	}
    	public BinaryIndexedTree2D(int[,] array)
    		: this(array.GetLength(0), array.GetLength(1))
    	{
    		for (var x = 0; x < X; x++) for (var y = 0; y < Y; y++) Add(x, y, array[x, y]);
    	}
    	public void Add(int x, int y, int value) { for (var i = x + 1; i <= X; i += i & (-i)) for (var j = y + 1; j <= Y; j += j & (-j)) bit[i, j] += value; }
    	public int Sum(int x0, int y0, int x1, int y1) { return Sum(x0, y0) + Sum(x1, y1) - Sum(x0, y1) - Sum(x1, y0); }
    	int Sum(int x, int y) { var sum = 0; for (var i = x; i > 0; i -= i & (-i)) for (var j = y; j > 0; j -= j & (-j)) sum += bit[i, j]; return sum; }
    }
    class BinaryIndexedTree
    {
    	public int Size { get; private set; }
    	int[] bit;
    	public BinaryIndexedTree(int size)
    	{
    		Size = size;
    		bit = new int[size + 1];
    	}
    	public BinaryIndexedTree(int[] array) : this(array.Length)
    	{
    		for (var i = 0; i < Size; i++) bit[i + 1] = array[i];
    		for (var i = 1; i < Size; i++) if (i + (i & (-i)) <= Size) bit[i + (i & (-i))] += bit[i];
    	}
    	// index is 0-indexed
    	public void Add(int index, int value) { for (var i = index + 1; i <= Size; i += i & (-i)) bit[i] += value; }
    	// from, to is 0-indexed
    	// from is inclusive, to is exclusive
    	public int Sum(int from, int to) { return Sum(to) - Sum(from); }
    	int Sum(int to) { var sum = 0; for (var i = to; i > 0; i -= i & (-i)) sum += bit[i]; return sum; }
    }
    class Amoeba
    {
    	public const int Dimension = 2;
    	public const double Alpha = 1;  // reflection
    	public const double Beta = 1 + 2.0 / Dimension; // expansion
    	public const double Gamma = 0.75 - 0.5 / Dimension; // contraction
    	public const double Delta = 1 - 1.0 / Dimension;    // shrink
    	public Pair<AmoebaState, double>[] a;
    	public AmoebaState m;
    	public void Initiate()
    	{
    		Array.Sort(a, (x, y) => x.Second.CompareTo(y.Second));
    		m = new AmoebaState();
    		for (var i = 0; i < Dimension; i++) m.Add(a[i].First);
    		m.Multiply(1.0 / Dimension);
    	}
    	void PartialSort(int i, int j) { if (a[i].Second > a[j].Second) a.Swap(i, j); }
    	void Accept(AmoebaState point, double value)
    	{
    		var tmp = Func.FirstBinary(0, Dimension, x => a[x].Second >= value);
    		if (tmp != Dimension) m.Add((point - a[Dimension - 1].First) / Dimension);
    		for (var i = Dimension; i > tmp; i--) a[i] = a[i - 1];
    		a[tmp].First = point;
    		a[tmp].Second = value;
    	}
    	public void Search()
    	{
    		var r = m + Alpha * (m - a[Dimension].First);
    		var fr = r.Func();
    		if (a[0].Second <= fr && fr < a[Dimension - 1].Second) { Accept(r, fr); return; }
    		var diff = r - m;
    		if (fr < a[0].Second)
    		{
    			var e = m + Beta * diff;
    			var fe = e.Func();
    			if (fe < fr) Accept(e, fe);
    			else Accept(r, fr);
    		}
    		else
    		{
    			var tmp = Gamma * diff;
    			var o = m + tmp;
    			var fo = o.Func();
    			var i = m - tmp;
    			var fi = i.Func();
    			if (fi < fo) { o = i; fo = fi; }
    			if (fo < a[Dimension - 1].Second) Accept(o, fo);
    			else Shrink();
    		}
    	}
    	void Shrink()
    	{
    		var tmp = (1 - Delta) * a[0].First;
    		for (var i = 1; i <= Dimension; i++) { a[i].First.Multiply(Delta); a[i].First.Add(tmp); a[i].Second = a[i].First.Func(); }
    		Initiate();
    	}
    }
    class AmoebaState
    {
    	public static int Dimension = 2;
    	public double[] vec;
    	public AmoebaState() { vec = new double[Dimension]; }
    	public AmoebaState(params double[] elements) : this() { elements.CopyTo(vec, 0); }
    	public double this[int n] { get { return vec[n]; } set { vec[n] = value; } }
    	public void Multiply(double r) { for (var i = 0; i < Dimension; i++) vec[i] *= r; }
    	public void Add(AmoebaState v) { for (var i = 0; i < Dimension; i++) vec[i] += v.vec[i]; }
    	public static AmoebaState operator +(AmoebaState p) { return new AmoebaState(p.vec); }
    	public static AmoebaState operator -(AmoebaState p) { var tmp = new AmoebaState(p.vec); tmp.Multiply(-1); return tmp; }
    	public static AmoebaState operator /(AmoebaState p, double r) { var tmp = new AmoebaState(p.vec); tmp.Multiply(1 / r); return tmp; }
    	public static AmoebaState operator *(double r, AmoebaState p) { var tmp = new AmoebaState(p.vec); tmp.Multiply(r); return tmp; }
    	public static AmoebaState operator *(AmoebaState p, double r) { return r * p; }
    	public static AmoebaState operator +(AmoebaState p, AmoebaState q) { var tmp = +p; tmp.Add(q); return tmp; }
    	public static AmoebaState operator -(AmoebaState p, AmoebaState q) { var tmp = -q; tmp.Add(p); return tmp; }
    	public double Func()
    	{
    		return 0;//P.Func(vec[0], vec[1]);
    	}
    	public static Problem P;
    }
    class BucketList<T> : ICollection<T>, IEnumerable<T>, ICollection, IEnumerable
    {
    	public Comparison<T> comp { get; protected set; }
    	public int BucketSize = 20;
    	public int Count { get { var sum = 0; var bucket = Head; while (bucket != null) { sum += bucket.Count; bucket = bucket.Next; } return sum; } }
    	public int NumOfBucket { get; protected set; }
    	public Bucket<T> Head { get; protected set; }
    	public Bucket<T> Tail { get; protected set; }
    	public BucketList(IComparer<T> comp) : this(comp.ToComparison()) { }
    	public BucketList(Comparison<T> comp = null) { Head = null; Tail = null; NumOfBucket = 0; this.comp = comp == null ? Func.DefaultComparison<T>() : comp; }
    	protected void AddAfter(Bucket<T> pos, Bucket<T> bucket)
    	{
    		Debug.Assert(bucket != null && bucket.Count > 0 && pos != null && pos.Parent == this && comp(pos.Tail.Value, bucket.Head.Value) <= 0
    					&& (pos.Next == null || comp(pos.Next.Head.Value, bucket.Tail.Value) >= 0));
    		bucket.Parent = this;
    		bucket.Prev = pos;
    		bucket.Next = pos.Next;
    		if (pos != Tail) pos.Next.Prev = bucket;
    		else Tail = bucket;
    		pos.Next = bucket;
    		NumOfBucket++;
    	}
    	protected void AddBefore(Bucket<T> pos, Bucket<T> bucket)
    	{
    		Debug.Assert(bucket != null && bucket.Count > 0 && pos != null && pos.Parent == this && comp(pos.Head.Value, bucket.Tail.Value) >= 0
    					&& (pos.Prev == null || comp(pos.Prev.Tail.Value, bucket.Head.Value) <= 0));
    		bucket.Parent = this;
    		bucket.Prev = pos.Prev;
    		bucket.Next = pos;
    		if (pos != Head) pos.Prev.Next = bucket;
    		else Head = bucket;
    		pos.Prev = bucket;
    		NumOfBucket++;
    	}
    	protected void AddAfter(Bucket<T> bucket, BucketNode<T> node)
    	{
    		Debug.Assert(node != null && bucket != null && bucket.Parent == this && node.Parent.Parent == this && comp(bucket.Tail.Value, node.Value) <= 0
    					&& (bucket.Next == null || comp(bucket.Next.Head.Value, node.Value) >= 0));
    		var tmp = new Bucket<T>(this, bucket, bucket.Next);
    		tmp.InitiateWith(node);
    		if (bucket != Tail) bucket.Next.Prev = tmp;
    		else Tail = tmp;
    		bucket.Next = tmp;
    		NumOfBucket++;
    	}
    	protected void AddBefore(Bucket<T> bucket, BucketNode<T> node)
    	{
    		Debug.Assert(node != null && bucket != null && bucket.Parent == this && node.Parent.Parent == this && comp(bucket.Head.Value, node.Value) >= 0
    					&& (bucket.Prev == null || comp(bucket.Prev.Tail.Value, node.Value) <= 0));
    		var tmp = new Bucket<T>(this, bucket.Prev, bucket);
    		tmp.InitiateWith(node);
    		if (bucket != Head) bucket.Prev.Next = tmp;
    		else Head = tmp;
    		bucket.Prev = tmp;
    		NumOfBucket++;
    	}
    	public void AddAfter(BucketNode<T> node, T item)
    	{
    		Debug.Assert(node != null && node.Parent.Parent == this && comp(node.Value, item) <= 0
    					&& ((node.Next == null && (node.Parent.Next == null || comp(node.Parent.Next.Head.Value, item) >= 0))
    						|| comp(node.Next.Value, item) >= 0));
    		var bucket = node.Parent;
    		var tmp = new BucketNode<T>(item, bucket, node, node.Next);
    		if (!bucket.AddAfter(node, tmp))
    		{
    			if (node.Next == null && (bucket.Next == null || bucket.Next.Count >= BucketSize)) AddAfter(bucket, tmp);
    			else if (node.Next == null) AddBefore(bucket.Next.Head, item);
    			else
    			{
    				node.Next.Prev = tmp;
    				node.Next = tmp;
    				while (node.Next.Next != null) node = node.Next;
    				item = node.Next.Value;
    				bucket.Tail = node;
    				node.Next = null;
    				AddAfter(node, item);
    			}
    		}
    	}
    	public void AddBefore(BucketNode<T> node, T item)
    	{
    		Debug.Assert(node != null && node.Parent.Parent == this && comp(node.Value, item) >= 0
    					&& ((node.Prev == null && (node.Parent.Prev == null || comp(node.Parent.Prev.Tail.Value, item) <= 0))
    						|| comp(node.Prev.Value, item) <= 0));
    		var bucket = node.Parent;
    		var tmp = new BucketNode<T>(item, bucket, node.Prev, node);
    		if (!bucket.AddBefore(node, tmp))
    		{
    			if (node.Prev == null && (bucket.Prev == null || bucket.Prev.Count >= BucketSize)) AddBefore(bucket, tmp);
    			else if (node.Prev == null) AddAfter(bucket.Prev.Tail, item);
    			else
    			{
    				node.Prev.Next = tmp;
    				node.Prev = tmp;
    				while (node.Prev.Prev != null) node = node.Prev;
    				item = node.Prev.Value;
    				bucket.Head = node;
    				node.Prev = null;
    				AddBefore(node, item);
    			}
    		}
    	}
    	// (node, index)
    	// index is the position of node in node.Parent
    	public Tuple<BucketNode<T>, int> UpperBound(Predicate<T> pred)
    	{
    		if (NumOfBucket == 0) return null;
    		if (pred(Tail.Tail.Value)) return new Tuple<BucketNode<T>, int>(Tail.Tail, Tail.Count - 1);
    		var bucket = Tail;
    		while (bucket.Prev != null && !pred(bucket.Prev.Tail.Value)) bucket = bucket.Prev;
    		var node = bucket.Tail;
    		var index = bucket.Count - 1;
    		while (node.Prev != null && !pred(node.Prev.Value)) { node = node.Prev; index--; }
    		if (node.Prev == null) return bucket.Prev == null ? null : new Tuple<BucketNode<T>, int>(bucket.Prev.Tail, bucket.Prev.Count - 1);
    		else return new Tuple<BucketNode<T>, int>(node.Prev, index - 1);
    	}
    	public Tuple<BucketNode<T>, int> UpperBound(T item) { return LowerBound(x => comp(x, item) <= 0); }
    	// (node, index)
    	// index is the position of node in node.Parent
    	public Tuple<BucketNode<T>, int> LowerBound(Predicate<T> pred)
    	{
    		if (NumOfBucket == 0) return null;
    		if (pred(Head.Head.Value)) return new Tuple<BucketNode<T>, int>(Head.Head, 0);
    		var bucket = Head;
    		while (bucket.Next != null && !pred(bucket.Next.Head.Value)) bucket = bucket.Next;
    		var node = bucket.Head;
    		var index = 0;
    		while (node.Next != null && !pred(node.Next.Value)) { node = node.Next; index++; }
    		if (node.Next == null) return bucket.Next == null ? null : new Tuple<BucketNode<T>, int>(bucket.Next.Head, 0);
    		else return new Tuple<BucketNode<T>, int>(node.Next, index + 1);
    	}
    	public Tuple<BucketNode<T>, int> LowerBound(T item) { return LowerBound(x => comp(x, item) >= 0); }
    	public void InitiateWith(Bucket<T> bucket)
    	{
    		Debug.Assert(bucket != null && bucket.Count > 0);
    		RemoveAll();
    		Head = Tail = bucket;
    		bucket.Parent = this;
    		NumOfBucket++;
    	}
    	public void InitiateWith(T item)
    	{
    		RemoveAll();
    		Head = Tail = new Bucket<T>(this, null, null);
    		Head.Head = Head.Tail = new BucketNode<T>(item, Head, null, null);
    		Head.Count++;
    		NumOfBucket++;
    	}
    	public void AddFirst(Bucket<T> bucket) { if (NumOfBucket == 0) InitiateWith(bucket); else AddBefore(Head, bucket); }
    	public void AddLast(Bucket<T> bucket) { if (NumOfBucket == 0) InitiateWith(bucket); else AddAfter(Tail, bucket); }
    	public void AddFirst(T item) { if (NumOfBucket == 0) InitiateWith(item); else AddBefore(Head.Head, item); }
    	public void AddLast(T item) { if (NumOfBucket == 0) InitiateWith(item); else AddAfter(Tail.Tail, item); }
    	public void Clear() { RemoveAll(); }
    	public void RemoveAll() { Head = Tail = null; NumOfBucket = 0; }
    	public void RemoveFirst() { if (NumOfBucket == 0) throw new InvalidOperationException(); else Remove(Head.Head); }
    	public void RemoveLast() { if (NumOfBucket == 0) throw new InvalidOperationException(); else Remove(Tail.Tail); }
    	// remove item and return whether item was removed or not
    	public bool Remove(T item) { var node = Find(item); if (node != null) Remove(node); return node != null; }
    	public void Remove(Bucket<T> bucket)
    	{
    		Debug.Assert(bucket != null && bucket.Parent == this);
    		NumOfBucket--;
    		if (bucket == Head && bucket == Tail) { Head = Tail = null; }
    		else if (bucket == Head) { Head.Next.Prev = null; Head = Head.Next; }
    		else if (bucket == Tail) { Tail.Prev.Next = null; Tail = Tail.Prev; }
    		else { bucket.Prev.Next = bucket.Next; bucket.Next.Prev = bucket.Prev; }
    	}
    	public void Remove(BucketNode<T> node) { Debug.Assert(node != null && node.Parent.Parent == this); if (!node.Parent.Remove(node)) Remove(node.Parent); }
    	protected void RemoveRange(Bucket<T> from, Bucket<T> to, int indexFrom = -1, int indexTo = -1)
    	{
    		Debug.Assert(from != null && to != null && from.Parent == this && to.Parent == this);
    		if (indexFrom < 0) indexFrom = from.Index;
    		if (indexTo < 0) indexTo = to.Index;
    		if (indexFrom == 0 && indexTo == NumOfBucket - 1) { Clear(); return; }
    		else if (indexFrom == 0) { Head = to.Next; Head.Prev = null; }
    		else if (indexTo == NumOfBucket - 1) { Tail = from.Prev; Tail.Next = null; }
    		else { from.Prev.Next = to.Next; to.Next.Prev = from.Prev; }
    		NumOfBucket -= indexTo - indexFrom + 1;
    	}
    	public void RemoveRange(BucketNode<T> from, BucketNode<T> to, int indexFrom = -1, int indexTo = -1)
    	{
    		Debug.Assert(from != null && to != null && from.Parent.Parent == this && to.Parent.Parent == this);
    		if (indexFrom < 0) indexFrom = from.Index;
    		if (indexTo < 0) indexTo = to.Index;
    		var bucketFrom = from.Parent;
    		var bucketTo = to.Parent;
    		if (bucketFrom == bucketTo)
    		{
    			var bucket = bucketFrom;
    			if (indexFrom == 0 && indexTo == bucket.Count - 1) Remove(bucket);
    			else bucket.RemoveRange(from, to, indexFrom, indexTo);
    		}
    		else
    		{
    			var bf = bucketFrom.Index;
    			var bt = bucketTo.Index;
    			Debug.Assert(bf < bt);
    			if (bt > bf + 1) RemoveRange(bucketFrom.Next, bucketTo.Prev, bf + 1, bt - 1);
    			if (indexFrom == 0) { Remove(bucketFrom); RemoveRange(bucketTo.Head, to, 0, indexTo); }
    			else if (indexTo == bucketTo.Count - 1) { Remove(bucketTo); RemoveRange(from, bucketFrom.Tail, indexFrom, bucketFrom.Count - 1); }
    			else
    			{
    				bucketFrom.RemoveRange(from, bucketFrom.Tail, indexFrom, bucketFrom.Count - 1);
    				bucketTo.RemoveRange(bucketTo.Head, to, 0, indexTo);
    				if (bucketFrom.Count + bucketTo.Count < BucketSize) Adjust();
    			}
    		}
    	}
    	public void Adjust()
    	{
    		var array = this.ToArray();
    		Clear();
    		var length = array.Length;
    		BucketSize = (int)Math.Sqrt(length + 1);
    		var count = (length + BucketSize - 1) / BucketSize;
    		for (var i = 0; i < count; i++)
    		{
    			var bucket = new Bucket<T>(this, null, null);
    			var lim = Math.Min(BucketSize * (i + 1), length);
    			for (var j = BucketSize * i; j < lim; j++) bucket.AddLast(array[j]);
    			AddLast(bucket);
    		}
    	}
    	public BucketNode<T> Find(T item) { var node = LowerBound(item); if (node == null || comp(node.Item1.Value, item) != 0) return null; else return node.Item1; }
    	public BucketNode<T> FindLast(T item) { var node = UpperBound(item); if (node == null || comp(node.Item1.Value, item) != 0) return null; else return node.Item1; }
    	public IEnumerator<T> GetEnumerator()
    	{
    		var bucket = Head;
    		while (bucket != null)
    		{
    			var node = bucket.Head;
    			while (node != null) { yield return node.Value; node = node.Next; }
    			bucket = bucket.Next;
    		}
    	}
    	public void Add(T item) { var ub = LowerBound(item); if (ub != null) AddBefore(ub.Item1, item); else AddLast(item); }
    	IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
    	public void CopyTo(Array array, int index) { foreach (var item in this) array.SetValue(item, index++); }
    	public bool IsSynchronized { get { return false; } }
    	public object SyncRoot { get { return this; } }
    	public bool IsReadOnly { get { return false; } }
    	public bool Contains(T item) { return Find(item) != null; }
    	public void CopyTo(T[] array, int index) { foreach (var item in this) array[index++] = item; }
    	public override string ToString()
    	{
    		var sb = new StringBuilder();
    		sb.Append("<Start>\n");
    		var node = Head;
    		while (node != null) { sb.Append(node.ToString() + "\n"); node = node.Next; }
    		sb.Append("<end>");
    		return sb.ToString();
    	}
    	public bool Check()
    	{
    		if (NumOfBucket == 0) return Head == null && Tail == null;
    		if (Head.Prev != null || Tail.Next != null) return false;
    		var bucket = Head;
    		var c = 1;
    		while (bucket.Next != null)
    		{
    			if (!CheckConnection(bucket) || !CheckBucket(bucket)) return false;
    			bucket = bucket.Next;
    			c++;
    		}
    		return bucket == Tail && CheckBucket(Tail) && c == NumOfBucket;
    	}
    	bool CheckConnection(Bucket<T> bucket)
    	{
    		if (bucket.Next == null) return bucket == Tail;
    		else return bucket.Next.Prev == bucket && comp(bucket.Tail.Value, bucket.Next.Head.Value) <= 0;
    	}
    	bool CheckBucket(Bucket<T> bucket) { return bucket.Count > 0 && bucket.Count <= BucketSize && bucket.Parent == this; }
    	public void Start(Func<string, T> parser, Func<T> random)
    	{
    		BucketNode<T> x = null, y = null;
    		var help = true;
    		while (true)
    		{
    			Console.Clear();
    			Console.WriteLine("{0} items, {1} buckets(size : {2})", Count, NumOfBucket, BucketSize);
    			Console.WriteLine(this);
    			Console.WriteLine(Check() ? "OK!" : "NG!");
    			if (help)
    			{
    				Console.WriteLine("when val is omitted, random value will be used.");
    				Console.WriteLine("a val : add val");
    				Console.WriteLine("r val : remove val");
    				Console.WriteLine("j : adjust");
    				Console.WriteLine("c : clear");
    				Console.WriteLine("h : disable/enable help message");
    				Console.WriteLine("x : set x");
    				Console.WriteLine("x h : set x to head");
    				Console.WriteLine("x t : set x to tail");
    				Console.WriteLine("x n : set x to x.next");
    				Console.WriteLine("x p : set x to x.prev");
    				Console.WriteLine("x f val : set x to lower bound of val");
    				Console.WriteLine("y : set y");
    				Console.WriteLine("x : exchange x and y");
    				Console.WriteLine("d : remove from x to y");
    				Console.WriteLine("q : quit");
    			}
    			if (x != null) Console.WriteLine("x = {0} <- {1}", x.Value, x.Parent);
    			if (y != null) Console.WriteLine("y = {0} <- {1}", y.Value, y.Parent);
    			Console.Write("enter command > ");
    			var command = Console.ReadLine().Split();
    			if (command[0].Length > 1 && command[0][1] == 'd')
    				Console.WriteLine("debug...");
    			if (command[0].StartsWith("a")) { if (command.Length > 1) Add(parser(command[1])); else Add(random()); }
    			else if (command[0].StartsWith("r")) { if (command.Length > 1) Remove(parser(command[1])); else Remove(random()); }
    			else if (command[0].StartsWith("c")) Clear();
    			else if (command[0].StartsWith("j")) Adjust();
    			else if (command[0].StartsWith("h")) help = !help;
    			else if (command[0].StartsWith("x")) SetVariable(command, ref x, parser, random);
    			else if (command[0].StartsWith("y")) SetVariable(command, ref y, parser, random);
    			else if (command[0].StartsWith("e")) { var tmp = x; x = y; y = tmp; }
    			else if (command[0].StartsWith("d")) { RemoveRange(x, y, x.Index, y.Index); x = null; y = null; }
    			else if (command[0].StartsWith("q")) break;
    		}
    	}
    	void SetVariable(string[] command, ref BucketNode<T> x, Func<string, T> parser, Func<T> random)
    	{
    		if (command[1].StartsWith("h")) x = Head.Head;
    		else if (command[1].StartsWith("t")) x = Tail.Tail;
    		else if (command[1].StartsWith("n"))
    		{
    			if (x.Next != null) x = x.Next;
    			else if (x.Parent.Next != null) x = x.Parent.Next.Head;
    			else { Console.WriteLine("x is the last element..."); Console.ReadKey(true); }
    		}
    		else if (command[1].StartsWith("p"))
    		{
    			if (x.Prev != null) x = x.Prev;
    			else if (x.Parent.Prev != null) x = x.Parent.Prev.Tail;
    			else { Console.WriteLine("x is the first element..."); Console.ReadKey(true); }
    		}
    		else if (command[1].StartsWith("f")) { if (command.Length > 2) x = LowerBound(parser(command[2])).Item1; else x = LowerBound(random()).Item1; }
    	}
    }
    // bucket cannot be empty
    class Bucket<T>
    {
    	public BucketList<T> Parent;
    	public int Count;
    	public Bucket<T> Prev;
    	public Bucket<T> Next;
    	public BucketNode<T> Head;
    	public BucketNode<T> Tail;
    	public Bucket(BucketList<T> parent, Bucket<T> prev, Bucket<T> next) { Parent = parent; Prev = prev; Next = next; Head = null; Tail = null; }
    	public int Index
    	{
    		get
    		{
    			var count = 0;
    			var node = Parent.Head;
    			while (node != this) { node = node.Next; count++; }
    			return count;
    		}
    	}
    	public bool AddAfter(BucketNode<T> node, BucketNode<T> item) { return AddAfter(node, item.Value); }
    	public bool AddBefore(BucketNode<T> node, BucketNode<T> item) { return AddBefore(node, item.Value); }
    	public bool AddAfter(BucketNode<T> node, T item)
    	{
    		Debug.Assert(node != null && node.Parent == this && Parent.comp(node.Value, item) <= 0
    					&& ((node.Next == null && (Next == null || Parent.comp(Next.Head.Value, item) >= 0))
    						|| Parent.comp(node.Next.Value, item) >= 0));
    		if (Count < Parent.BucketSize)
    		{
    			var tmp = new BucketNode<T>(item, this, node, node.Next);
    			if (node.Next != null) node.Next.Prev = tmp;
    			else Tail = tmp;
    			node.Next = tmp;
    			Count++;
    			return true;
    		}
    		return false;
    	}
    	public bool AddBefore(BucketNode<T> node, T item)
    	{
    		Debug.Assert(node != null && node.Parent == this && Parent.comp(node.Value, item) >= 0
    					&& ((node.Prev == null && (Prev == null || Parent.comp(Prev.Tail.Value, item) <= 0))
    						|| Parent.comp(node.Prev.Value, item) <= 0));
    		if (Count < Parent.BucketSize)
    		{
    			var tmp = new BucketNode<T>(item, this, node.Prev, node);
    			if (node.Prev != null) node.Prev.Next = tmp;
    			else Head = tmp;
    			node.Prev = tmp;
    			Count++;
    			return true;
    		}
    		else return false;
    	}
    	public bool InitiateWith(BucketNode<T> node)
    	{
    		Head = Tail = node;
    		node.Parent = this;
    		node.Prev = node.Next = null;
    		Count++;
    		return true;
    	}
    	public bool InitiateWith(T item) { return InitiateWith(new BucketNode<T>(item, this, null, null)); }
    	public void RemoveAll() { Head = Tail = null; Count = 0; }
    	public bool AddFirst(T item) { if (Count == 0) return InitiateWith(item); else return AddBefore(Head, item); }
    	public bool AddLast(T item) { if (Count == 0) return InitiateWith(item); else return AddAfter(Tail, item); }
    	public bool Remove(BucketNode<T> node)
    	{
    		Debug.Assert(node != null && node.Parent == this);
    		if (Count > 1)
    		{
    			Count--;
    			if (node == Head) { Head.Next.Prev = null; Head = Head.Next; }
    			else if (node == Tail) { Tail.Prev.Next = null; Tail = Tail.Prev; }
    			else { node.Prev.Next = node.Next; node.Next.Prev = node.Prev; }
    			return true;
    		}
    		else return false;
    	}
    	public bool RemoveRange(BucketNode<T> from, BucketNode<T> to, int indexFrom = -1, int indexTo = -1)
    	{
    		Debug.Assert(from != null && to != null && from.Parent == this && to.Parent == this);
    		if (indexFrom < 0) indexFrom = from.Index;
    		if (indexTo < 0) indexTo = to.Index;
    		if (indexTo == 0 && indexFrom == Count - 1) return false;
    		else if (indexFrom == 0) { Head = to.Next; Head.Prev = null; }
    		else if (indexTo == Count - 1) { Tail = from.Prev; Tail.Next = null; }
    		else { from.Prev.Next = to.Next; to.Next.Prev = from.Prev; }
    		Count -= indexTo - indexFrom + 1;
    		return true;
    	}
    	public override string ToString()
    	{
    		var sb = new StringBuilder();
    		sb.Append("[");
    		var node = Head;
    		while (node != null) { sb.Append(node.ToString() + ", "); node = node.Next; }
    		if (sb.Length > 1) sb.Remove(sb.Length - 2, 2);
    		sb.Append("]");
    		return sb.ToString();
    	}
    	public bool Check()
    	{
    		if (Count == 0) return Head == null && Tail == null;
    		if (Head.Prev != null || Tail.Next != null) return false;
    		var node = Head;
    		var c = 1;
    		while (node.Next != null)
    		{
    			if (!CheckConnection(node) || !CheckNode(node)) return false;
    			node = node.Next;
    			c++;
    		}
    		return node == Tail && CheckNode(Tail) && c == Count;
    	}
    	bool CheckConnection(BucketNode<T> node)
    	{
    		if (node.Next == null) return node == Tail;
    		else return node.Next.Prev == node && Parent.comp(node.Value, node.Next.Value) <= 0;
    	}
    	bool CheckNode(BucketNode<T> node) { return node.Parent == this; }
    }
    class BucketNode<T>
    {
    	public T Value;
    	public Bucket<T> Parent;
    	public BucketNode<T> Prev;
    	public BucketNode<T> Next;
    	public BucketNode(T item, Bucket<T> parent, BucketNode<T> prev, BucketNode<T> next) { Value = item; Parent = parent; Prev = prev; Next = next; }
    	public int Index
    	{
    		get
    		{
    			var count = 0;
    			var node = Parent.Head;
    			while (node != this) { node = node.Next; count++; }
    			return count;
    		}
    	}
    	public override string ToString() { return Value.ToString(); }
    }
    class UndirectedGraph<V, E> : DirectedGraph<V, E>
    {
    	public UndirectedGraph(int V) : base(V) { }
    	public UndirectedGraph(int V, IEnumerable<EdgeInfo<E>> edges) : base(V, edges) { }
    	public override void AddEdge(EdgeInfo<E> edge)
    	{
    		edges.Add(edge);
    		edges.Add(edge.Reverse());
    		edgesFrom[edge.From].Add(new HalfEdgeInfo<E>(edge.To, edge.Information));
    		edgesFrom[edge.To].Add(new HalfEdgeInfo<E>(edge.From, edge.Information));
    		edgesTo[edge.To].Add(new HalfEdgeInfo<E>(edge.From, edge.Information));
    		edgesTo[edge.From].Add(new HalfEdgeInfo<E>(edge.To, edge.Information));
    	}
    	public bool IsConnected
    	{
    		get
    		{
    			if (numberOfNodes == 0) return true;
    			var used = new bool[numberOfNodes];
    			var queue = new Queue<int>();
    			queue.Enqueue(0);
    			while (queue.Count > 0)
    			{
    				var v = queue.Dequeue();
    				if (used[v]) continue;
    				used[v] = true;
    				foreach (var e in EdgesFrom(v)) queue.Enqueue(e.End);
    			}
    			return used.All(x => x);
    		}
    	}
    	public bool IsTree
    	{
    		get
    		{
    			if (numberOfNodes == 0) return true;
    			var used = new bool[numberOfNodes];
    			var queue = new Queue<int>();
    			queue.Enqueue(0);
    			while (queue.Count > 0)
    			{
    				var v = queue.Dequeue();
    				if (used[v]) return false;
    				used[v] = true;
    				foreach (var e in EdgesFrom(v)) queue.Enqueue(e.End);
    			}
    			return used.All(x => x);
    		}
    	}
    	public UndirectedGraph<V, E> MinimumSpanningTreePrim(int start, Func<E, int> cost)
    	{
    		var graph = new UndirectedGraph<V, E>(numberOfNodes);
    		nodes.CopyTo(graph.nodes, 0);
    		var d = Enumerable.Repeat(Func.Inf, numberOfNodes).ToArray();
    		var used = new bool[numberOfNodes];
    		var queue = new PriorityQueue<Pair<EdgeInfo<E>, int>>((x, y) => x.Second.CompareTo(y.Second), numberOfNodes);
    		d[start] = 0;
    		queue.Enqueue(new Pair<EdgeInfo<E>, int>(new EdgeInfo<E>(-1, 0, default(E)), 0));
    		while (queue.Count > 0)
    		{
    			var p = queue.Dequeue();
    			var v = p.First.To;
    			if (d[v] < p.Second) continue;
    			used[v] = true;
    			if (p.First.From >= 0) graph.AddEdge(v, p.First.From, p.First.Information);
    			foreach (var w in EdgesFrom(v))
    			{
    				if (!used[w.End] && cost(w.Information) < d[w.End])
    				{
    					d[w.End] = cost(w.Information);
    					queue.Enqueue(new Pair<EdgeInfo<E>, int>(new EdgeInfo<E>(v, w.End, w.Information), cost(w.Information)));
    				}
    			}
    		}
    		return graph;
    	}
    	public UndirectedGraph<V, E> MinimumSpanningTreeKruskal(Func<E, int> cost)
    	{
    		var graph = new UndirectedGraph<V, E>(numberOfNodes);
    		nodes.CopyTo(graph.nodes, 0);
    		var tree = new UnionFindTree(numberOfNodes);
    		edges.Sort((x, y) => cost(x.Information).CompareTo(cost(y.Information)));
    		foreach (var e in edges)
    		{
    			if (!tree.IsSameCategory(e.From, e.To))
    			{
    				tree.UniteCategory(e.From, e.To);
    				graph.AddEdge(e);
    			}
    		}
    		return graph;
    	}
    	public bool IsBipartite
    	{
    		get
    		{
    			var color = new int[numberOfNodes];
    			foreach (var v in nodes)
    			{
    				if (color[v.Code] == 0)
    				{
    					var queue = new Queue<Pair<int, int>>();
    					queue.Enqueue(new Pair<int, int>(v.Code, 1));
    					while (queue.Count > 0)
    					{
    						var w = queue.Dequeue();
    						if (color[w.First] != 0)
    						{
    							if (color[w.First] != w.Second)
    								return false;
    							continue;
    						}
    						color[w.First] = w.Second;
    						foreach (var e in EdgesFrom(w.First)) queue.Enqueue(new Pair<int, int>(e.End, -w.Second));
    					}
    				}
    			}
    			return true;
    		}
    	}
    	public IEnumerable<NodeInfo<V>> GetArticulationPoints()
    	{
    		var visited = new bool[numberOfNodes];
    		var parent = new int[numberOfNodes];
    		var children = Enumerable.Range(0, numberOfNodes).Select(_ => new SortedSet<int>()).ToArray();
    		var order = new int[numberOfNodes];
    		var lowest = new int[numberOfNodes];
    		var isroot = new bool[numberOfNodes];
    		var count = 1;
    		var isarticulation = new bool[numberOfNodes];
    		Action<int, int> dfs = null;
    		dfs = (u, prev) =>
    		{
    			order[u] = count;
    			lowest[u] = count;
    			count++;
    			visited[u] = true;
    			foreach (var e in edgesFrom[u])
    			{
    				var v = e.End;
    				if (visited[v]) { if (v != prev) lowest[u] = Math.Min(lowest[u], order[v]); }
    				else
    				{
    					parent[v] = u;
    					if (isroot[u]) children[u].Add(v);
    					dfs(v, u);
    					lowest[u] = Math.Min(lowest[u], lowest[v]);
    					if (order[u] <= lowest[v]) isarticulation[u] = true;
    				}
    			}
    		};
    		for (var v = 0; v < numberOfNodes; v++)
    		{
    			if (visited[v]) continue;
    			count = 1; dfs(v, -1);
    			isroot[v] = true;
    		}
    		for (var v = 0; v < numberOfNodes; v++)
    		{
    			if (isroot[v]) { if (children[v].Count > 1) yield return nodes[v]; }
    			else { if (isarticulation[v]) yield return nodes[v]; }
    		}
    	}
    	public string ToString(Func<NodeInfo<V>, string> vertex, Func<EdgeInfo<E>, string> edge)
    	{
    		var sb = new StringBuilder();
    		sb.Append("graph G {\n");
    		foreach (var v in nodes) sb.Append("\tv" + v.Code + " [label = \"" + vertex(v) + "\"];\n");
    		foreach (var e in edges) sb.Append("\tv" + e.From + " -- v" + e.To + " [label=\"" + edge(e) + "\"];\n");
    		sb.Append("}");
    		return sb.ToString();
    	}
    	public override string ToString() { return ToString(v => v.ToString(), e => e.ToString()); }
    }
    class NodeInfo<V> : Pair<int, V>
    {
    	public int Code { get { return First; } set { First = value; } }
    	public V Information { get { return Second; } set { Second = value; } }
    	public NodeInfo() : base() { }
    	public NodeInfo(int code, V info) : base(code, info) { }
    }
    class HalfEdgeInfo<E> : Pair<int, E>
    {
    	public int End { get { return First; } set { First = value; } }
    	public E Information { get { return Second; } set { Second = value; } }
    	public HalfEdgeInfo() : base() { }
    	public HalfEdgeInfo(int end, E info) : base(end, info) { }
    }
    class EdgeInfo<E> : Pair<Pair<int, int>, E>
    {
    	public int From { get { return First.First; } set { First.First = value; } }
    	public int To { get { return First.Second; } set { First.Second = value; } }
    	public E Information { get { return Second; } set { Second = value; } }
    	public EdgeInfo() : base() { }
    	public EdgeInfo(int from, int to, E info) : base(new Pair<int, int>(from, to), info) { }
    	public EdgeInfo<E> Reverse() { return new EdgeInfo<E>(To, From, Information); }
    }
    class DirectedGraph<V, E> : IEnumerable<NodeInfo<V>>
    {
    	protected int numberOfNodes;
    	public int NumberOfNodes { get { return numberOfNodes; } }
    	protected NodeInfo<V>[] nodes;
    	protected List<EdgeInfo<E>> edges;
    	protected List<HalfEdgeInfo<E>>[] edgesFrom;
    	protected List<HalfEdgeInfo<E>>[] edgesTo;
    	public IEnumerable<HalfEdgeInfo<E>> EdgesFrom(int node) { return edgesFrom[node]; }
    	public int InDegree(int node) { return edgesTo[node].Count; }
    	public int OutDegree(int node) { return edgesFrom[node].Count; }
    	public IEnumerable<HalfEdgeInfo<E>> EdgesTo(int node) { return edgesTo[node]; }
    	public V this[int node] { get { return nodes[node].Second; } set { nodes[node].Second = value; } }
    	public IEnumerable<EdgeInfo<E>> Edges { get { return edges; } }
    	public DirectedGraph(int V)
    	{
    		numberOfNodes = V;
    		nodes = Enumerable.Range(0, V).Select(x => new NodeInfo<V>(x, default(V))).ToArray();
    		edges = new List<EdgeInfo<E>>();
    		edgesFrom = Enumerable.Range(0, V).Select(_ => new List<HalfEdgeInfo<E>>()).ToArray();
    		edgesTo = Enumerable.Range(0, V).Select(_ => new List<HalfEdgeInfo<E>>()).ToArray();
    	}
    	public DirectedGraph(int V, IEnumerable<EdgeInfo<E>> edges) : this(V) { foreach (var e in edges) AddEdge(e.From, e.To, e.Information); }
    	public virtual void AddEdge(EdgeInfo<E> edge)
    	{
    		edges.Add(edge);
    		edgesFrom[edge.From].Add(new HalfEdgeInfo<E>(edge.To, edge.Information));
    		edgesTo[edge.To].Add(new HalfEdgeInfo<E>(edge.From, edge.Information));
    	}
    	public void AddEdge(int from, int to, E information) { AddEdge(new EdgeInfo<E>(from, to, information)); }
    	public void AddEdge(V from, V to, E information) { AddEdge(new EdgeInfo<E>(SearchNode(from).Code, SearchNode(to).Code, information)); }
    	public NodeInfo<V> SearchNode(V node) { return nodes.FirstOrDefault(e => e.Information.Equals(node)); }
    	public EdgeInfo<E> SearchEdge(E edge) { return edges.Find(e => e.Information.Equals(edge)); }
    	public IEnumerator<NodeInfo<V>> GetEnumerator() { foreach (var v in nodes) yield return v; }
    	IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
    	public int[] ShortestPathLengthFrom(int from, Func<E, int> cost)
    	{
    		var d = Enumerable.Repeat(Func.Inf, numberOfNodes).ToArray();
    		d[from] = 0;
    		var update = true;
    		while (update)
    		{
    			update = false;
    			foreach (var e in edges)
    			{
    				var tmp = d[e.From] + cost(e.Information);
    				if (d[e.From] < Func.Inf && d[e.To] > tmp)
    				{
    					d[e.To] = tmp;
    					update = true;
    				}
    			}
    		}
    		return d;
    	}
    	public int[] DijkstraFrom(int from, Func<E, int> cost)
    	{
    		var d = Enumerable.Repeat(Func.Inf, numberOfNodes).ToArray();
    		var queue = new PriorityQueue<Pair<int, int>>((x, y) => x.Second.CompareTo(y.Second));
    		d[from] = 0;
    		queue.Enqueue(new Pair<int, int>(from, 0));
    		while (!queue.IsEmpty)
    		{
    			var p = queue.Dequeue();
    			var v = p.First;
    			if (d[v] < p.Second) continue;
    			foreach (var e in EdgesFrom(v))
    			{
    				var tmp = d[v] + cost(e.Information);
    				if (d[e.End] > tmp) queue.Enqueue(new Pair<int, int>(e.End, d[e.End] = tmp));
    			}
    		}
    		return d;
    	}
    	// cost(e)>=0
    	public long[] DijkstraFromL(int from, Func<E, long> cost)
    	{
    		var d = Enumerable.Repeat(Func.InfL, numberOfNodes).ToArray();
    		var queue = new PriorityQueue<Pair<int, long>>((x, y) => x.Second.CompareTo(y.Second));
    		d[from] = 0;
    		queue.Enqueue(new Pair<int, long>(from, 0));
    		while (!queue.IsEmpty)
    		{
    			var p = queue.Dequeue();
    			var v = p.First;
    			if (d[v] < p.Second) continue;
    			foreach (var e in EdgesFrom(v))
    			{
    				var tmp = d[v] + cost(e.Information);
    				if (d[e.End] > tmp) queue.Enqueue(new Pair<int, long>(e.End, d[e.End] = tmp));
    			}
    		}
    		return d;
    	}
    	public int[,] ShortestPathLengthEachOther(Func<E, int> cost)
    	{
    		var d = new int[numberOfNodes, numberOfNodes];
    		for (var v = 0; v < numberOfNodes; v++) for (var w = 0; w < numberOfNodes; w++) d[v, w] = Func.Inf;
    		for (var v = 0; v < numberOfNodes; v++) d[v, v] = 0;
    		foreach (var e in edges) if (e.From != e.To) d[e.From, e.To] = cost(e.Information);
    		for (var k = 0; k < numberOfNodes; k++)
    			for (var v = 0; v < numberOfNodes; v++)
    				for (var w = 0; w < numberOfNodes; w++)
    					d[v, w] = Math.Min(d[v, w], d[v, k] + d[k, w]);
    		return d;
    	}
    	public bool ContainsNegativeLoopWF(Func<E, int> cost)
    	{
    		var d = ShortestPathLengthEachOther(cost);
    		for (var v = 0; v < numberOfNodes; v++) if (d[v, v] < 0) return true;
    		return false;
    	}
    	public bool ContainsNegativeLoop(Func<E, int> cost)
    	{
    		var d = Enumerable.Repeat(0, numberOfNodes).ToArray();
    		for (var v = 0; v < numberOfNodes; v++)
    		{
    			foreach (var e in edges)
    			{
    				var tmp = d[e.From] + cost(e.Information);
    				if (d[e.To] > tmp)
    				{
    					d[e.To] = tmp;
    					if (v == numberOfNodes - 1) return true;
    				}
    			}
    		}
    		return false;
    	}
    	public IEnumerable<int> ReachableFrom(int from)
    	{
    		var used = new bool[numberOfNodes];
    		var queue = new Queue<int>();
    		queue.Enqueue(from);
    		while (queue.Count > 0)
    		{
    			var v = queue.Dequeue();
    			if (used[v]) continue;
    			used[v] = true;
    			foreach (var e in EdgesFrom(v)) queue.Enqueue(e.End);
    		}
    		for (var v = 0; v < numberOfNodes; v++) if (used[v]) yield return v;
    	}
    	public bool IsReachable(int from, int to)
    	{
    		var used = new bool[numberOfNodes];
    		var queue = new Queue<int>();
    		queue.Enqueue(from);
    		while (queue.Count > 0)
    		{
    			var v = queue.Dequeue();
    			if (v == to) return true;
    			if (used[v]) continue;
    			used[v] = true;
    			foreach (var e in EdgesFrom(v)) queue.Enqueue(e.End);
    		}
    		return false;
    	}
    	public Pair<DirectedGraph<HashSet<NodeInfo<V>>, object>, int[]> StronglyConnectedComponents()
    	{
    		var mark = new bool[numberOfNodes];
    		var stack = new Stack<int>();
    		Action<int> dfs = null;
    		dfs = v =>
    		{
    			mark[v] = true;
    			foreach (var w in edgesFrom[v]) if (!mark[w.End]) dfs(w.End);
    			stack.Push(v);
    		};
    		for (var v = 0; v < numberOfNodes; v++) if (!mark[v]) dfs(v);
    		var scc = new List<HashSet<NodeInfo<V>>>();
    		mark = new bool[numberOfNodes];
    		var which = new int[numberOfNodes];
    		Action<int, HashSet<NodeInfo<V>>> rdfs = null;
    		rdfs = (v, set) =>
    		{
    			set.Add(new NodeInfo<V>(v, nodes[v].Information));
    			mark[v] = true;
    			foreach (var w in edgesFrom[v]) if (!mark[w.End]) rdfs(w.End, set);
    		};
    		var M = 0;
    		while (stack.Count > 0)
    		{
    			var v = stack.Pop();
    			if (mark[v]) continue;
    			var set = new HashSet<NodeInfo<V>>();
    			rdfs(v, set);
    			scc.Add(set);
    			foreach (var w in set) which[w.Code] = M;
    			M++;
    		}
    		var graph = new UndirectedGraph<HashSet<NodeInfo<V>>, object>(M);
    		for (var v = 0; v < M; v++) graph[v] = scc[v];
    		foreach (var e in edges) if (which[e.From] != which[e.To]) graph.AddEdge(which[e.From], which[e.To], null);
    		return new Pair<DirectedGraph<HashSet<NodeInfo<V>>, object>, int[]>(graph, which);
    	}
    	public string ToString(Func<V, string> vertex, Func<E, string> edge)
    	{
    		var sb = new StringBuilder();
    		sb.Append("digraph G {\n");
    		foreach (var v in nodes) sb.Append("\tv" + v.Code + " [label = \"" + vertex(v.Information) + "\"];\n");
    		foreach (var e in edges) sb.Append("\tv" + e.From + " -> v" + e.To + " [label=\"" + edge(e.Information) + "\"];\n");
    		sb.Append("}");
    		return sb.ToString();
    	}
    	public override string ToString() { return ToString(v => v.ToString(), e => e.ToString()); }
    }
    class UnionFindTree
    {
    	int N;
    	int[] parent, rank, size;
    	public UnionFindTree(int capacity)
    	{
    		N = capacity;
    		parent = new int[N];
    		rank = new int[N];
    		size = new int[N];
    		for (var i = 0; i < N; i++) { parent[i] = i; size[i] = 1; }
    	}
    	public int GetSize(int x) { return size[GetRootOf(x)]; }
    	public int GetRootOf(int x) { return parent[x] == x ? x : parent[x] = GetRootOf(parent[x]); }
    	public bool UniteCategory(int x, int y)
    	{
    		if ((x = GetRootOf(x)) == (y = GetRootOf(y))) return false;
    		if (rank[x] < rank[y]) { parent[x] = y; size[y] += size[x]; }
    		else
    		{
    			parent[y] = x; size[x] += size[y];
    			if (rank[x] == rank[y]) rank[x]++;
    		}
    		return true;
    	}
    	public bool IsSameCategory(int x, int y) { return GetRootOf(x) == GetRootOf(y); }
    }
    class AVLTree<T> : IEnumerable<T>, ICollection<T>, ICollection, IEnumerable
    {
    	public class AVLNode : IEnumerable<T>
    	{
    		AVLTree<T> tree;
    		int height;
    		public int Height { get { return height; } }
    		public int Bias { get { return Left.height - Right.height; } }
    		public T Item;
    		public AVLNode Parent;
    		public AVLNode Left;
    		public AVLNode Right;
    		AVLNode(T x, AVLTree<T> tree) { this.tree = tree; Item = x; Left = tree.sentinel; Right = tree.sentinel; }
    		public AVLNode(AVLTree<T> tree) : this(default(T), tree) { height = 0; Parent = null; }
    		public AVLNode(T x, AVLNode parent, AVLTree<T> tree) : this(x, tree) { this.height = 1; this.Parent = parent; }
    		public void Adjust() { height = 1 + Math.Max(Left.height, Right.height); }
    		public void ResetAsSentinel() { height = 0; Left = tree.sentinel; Right = tree.sentinel; }
    		public IEnumerator<T> GetEnumerator()
    		{
    			if (this != tree.sentinel)
    			{
    				foreach (var x in Left) yield return x;
    				yield return Item;
    				foreach (var x in Right) yield return x;
    			}
    		}
    		IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
    	}
    	AVLNode sentinel;
    	Comparison<T> comp;
    	Func<T, T, bool> equals;
    	int count;
    	// assumed to be comparer
    	// i.e. comp(x,x)=0, and comp(x,y)>0 then comp(y,x)<0, and comp(x,y)>0 & comp(y,z)>0 then comp(x,z)>0
    	public AVLTree(Comparison<T> comp)
    	{
    		sentinel = new AVLNode(this);
    		sentinel.ResetAsSentinel();
    		this.comp = comp == null ? Func.DefaultComparison<T>() : comp;
    		if (typeof(T).IsValueType) equals = (x, y) => x.Equals(y);
    		else equals = (x, y) => ReferenceEquals(x, y);
    		count = 0;
    	}
    	public AVLTree(IComparer<T> comp = null) : this(comp.ToComparison()) { }
    	void Replace(AVLNode u, AVLNode v)
    	{
    		var parent = u.Parent;
    		if (parent.Left == u) parent.Left = v;
    		else parent.Right = v;
    		v.Parent = parent;
    	}
    	AVLNode RotateL(AVLNode v)
    	{
    		var u = v.Right;
    		Replace(v, u);
    		v.Right = u.Left;
    		u.Left.Parent = v;
    		u.Left = v;
    		v.Parent = u;
    		v.Adjust();
    		u.Adjust();
    		return u;
    	}
    	AVLNode RotateR(AVLNode u)
    	{
    		var v = u.Left;
    		Replace(u, v);
    		u.Left = v.Right;
    		v.Right.Parent = u;
    		v.Right = u;
    		u.Parent = v;
    		u.Adjust();
    		v.Adjust();
    		return v;
    	}
    	AVLNode RotateLR(AVLNode t) { RotateL(t.Left); return RotateR(t); }
    	AVLNode RotateRL(AVLNode t) { RotateR(t.Right); return RotateL(t); }
    	void Adjust(bool isInsertMode, AVLNode node)
    	{
    		while (node.Parent != sentinel)
    		{
    			var parent = node.Parent;
    			var height = parent.Height;
    			if ((parent.Left == node) == isInsertMode)
    				if (parent.Bias == 2)
    					if (parent.Left.Bias >= 0) parent = RotateR(parent);
    					else parent = RotateLR(parent);
    				else parent.Adjust();
    			else
    				if (parent.Bias == -2)
    				if (parent.Right.Bias <= 0) parent = RotateL(parent);
    				else parent = RotateRL(parent);
    			else parent.Adjust();
    			if (height == parent.Height) break;
    			node = parent;
    		}
    	}
    	public void Add(T item)
    	{
    		var parent = sentinel;
    		var pos = sentinel.Left;
    		var isLeft = true;
    		count++;
    		while (pos != sentinel)
    			if (comp(item, pos.Item) < 0) { parent = pos; pos = pos.Left; isLeft = true; }
    			else { parent = pos; pos = pos.Right; isLeft = false; }
    		if (isLeft)
    		{
    			parent.Left = new AVLNode(item, parent, this);
    			Adjust(true, parent.Left);
    		}
    		else
    		{
    			parent.Right = new AVLNode(item, parent, this);
    			Adjust(true, parent.Right);
    		}
    	}
    	// if equals(x,y) holds then !(comp(x,y)<0) and !(comp(x,y)>0) must hold
    	// i.e. equals(x,y) -> comp(x,y)=0
    	public bool Remove(T item, AVLNode start)
    	{
    		var pos = start;
    		while (pos != sentinel)
    		{
    			if (comp(item, pos.Item) < 0) pos = pos.Left;
    			else if (comp(item, pos.Item) > 0) pos = pos.Right;
    			else if (equals(pos.Item, item))
    			{
    				if (pos.Left == sentinel)
    				{
    					Replace(pos, pos.Right);
    					Adjust(false, pos.Right);
    				}
    				else
    				{
    					var max = Max(pos.Left);
    					pos.Item = max.Item;
    					Replace(max, max.Left);
    					Adjust(false, max.Left);
    				}
    				count--;
    				return true;
    			}
    			else return Remove(item, pos.Left) || Remove(item, pos.Right);
    		}
    		return false;
    	}
    	public bool Remove(T item) { return Remove(item, sentinel.Left); }
    	AVLNode Max(AVLNode node)
    	{
    		while (node.Right != sentinel) node = node.Right;
    		return node;
    	}
    	AVLNode Min(AVLNode node)
    	{
    		while (node.Left != sentinel) node = node.Left;
    		return node;
    	}
    	public bool Contains(T item)
    	{
    		var pos = sentinel.Left;
    		while (pos != sentinel)
    		{
    			if (comp(item, pos.Item) < 0) pos = pos.Left;
    			else if (comp(item, pos.Item) > 0) pos = pos.Right;
    			else return true;
    		}
    		return false;
    	}
    	public T Find(T item)
    	{
    		var pos = sentinel.Left;
    		while (pos != sentinel)
    		{
    			if (comp(item, pos.Item) < 0) pos = pos.Left;
    			else if (comp(item, pos.Item) > 0) pos = pos.Right;
    			else return pos.Item;
    		}
    		return default(T);
    	}
    	public AVLNode LowerBound(Predicate<T> pred) { AVLNode node; LowerBound(pred, sentinel.Left, out node); return node; }
    	public AVLNode UpperBound(Predicate<T> pred) { AVLNode node; UpperBound(pred, sentinel.Left, out node); return node; }
    	public AVLNode LowerBound(T item) { return LowerBound(x => comp(x, item) >= 0); }
    	public AVLNode UpperBound(T item) { return UpperBound(x => comp(x, item) <= 0); }
    	bool UpperBound(Predicate<T> pred, AVLNode node, out AVLNode res)
    	{
    		if (node == sentinel) { res = null; return false; }
    		if (pred(node.Item)) { if (!UpperBound(pred, node.Right, out res)) res = node; return true; }
    		else return UpperBound(pred, node.Left, out res);
    	}
    	bool LowerBound(Predicate<T> pred, AVLNode node, out AVLNode res)
    	{
    		if (node == sentinel) { res = null; return false; }
    		if (pred(node.Item)) { if (!LowerBound(pred, node.Left, out res)) res = node; return true; }
    		else return LowerBound(pred, node.Right, out res);
    	}
    	public T Min() { return Min(sentinel.Left).Item; }
    	public AVLNode MinNode() { return Min(sentinel.Left); }
    	public T Max() { return Max(sentinel.Left).Item; }
    	public AVLNode MaxNode() { return Max(sentinel.Left); }
    	public bool IsEmpty { get { return sentinel.Left == sentinel; } }
    	public void Clear() { sentinel.Left = sentinel; count = 0; sentinel.ResetAsSentinel(); }
    	public IEnumerator<T> GetEnumerator() { return sentinel.Left.GetEnumerator(); }
    	IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
    	public void CopyTo(T[] array, int arrayIndex) { foreach (var x in this) array[arrayIndex++] = x; }
    	public int Count { get { return count; } }
    	public bool IsReadOnly { get { return true; } }
    	public void CopyTo(Array array, int index) { foreach (var x in this) array.SetValue(x, index++); }
    	public bool IsSynchronized { get { return false; } }
    	public object SyncRoot { get { return this; } }
    	public override string ToString()
    	{
    		var nodes = new StringBuilder();
    		var edges = new StringBuilder();
    		ConcatSubTree(nodes, edges, sentinel.Left, "L");
    		return "digraph G {\n" + nodes.ToString() + edges.ToString() + "}";
    	}
    	void ConcatSubTree(StringBuilder nodes, StringBuilder edges, AVLNode node, string code)
    	{
    		if (node == sentinel) return;
    		nodes.Append("\tv" + code + " [label = \"" + node.Height + ":" + node.Item + "\"];\n");
    		if (node.Left != sentinel) edges.Append("\tv" + code + " -> v" + code + "L;\n");
    		if (node.Right != sentinel) edges.Append("\tv" + code + " -> v" + code + "R;\n");
    		ConcatSubTree(nodes, edges, node.Left, code + "L");
    		ConcatSubTree(nodes, edges, node.Right, code + "R");
    	}
    	public bool IsBalanced() { return IsBalanced(sentinel.Left); }
    	public bool IsValidBinarySearchTree() { return IsValidBinarySearchTree(sentinel.Left); }
    	bool IsBalanced(AVLNode node) { return node == sentinel || (Math.Abs(node.Bias) < 2 && IsBalanced(node.Left) && IsBalanced(node.Right)); }
    	bool IsValidBinarySearchTree(AVLNode node)
    	{
    		return node == sentinel || (Small(node.Item, node.Left) && Large(node.Item, node.Right)
    			&& IsValidBinarySearchTree(node.Left) && IsValidBinarySearchTree(node.Right));
    	}
    	bool Small(T item, AVLNode node) { return node == sentinel || (comp(item, node.Item) >= 0 && Small(item, node.Left) && Small(item, node.Right)); }
    	bool Large(T item, AVLNode node) { return node == sentinel || (comp(item, node.Item) <= 0 && Large(item, node.Left) && Large(item, node.Right)); }
    	public static void CheckAVL(Random rand, int N)
    	{
    		Comparison<double> comp = (x, y) => x.CompareTo(y);
    		var avl = new AVLTree<double>(comp);
    		var toBeLeft = new double[N];
    		var toBeRemoved = new double[N];
    		for (var i = 0; i < N; i++) avl.Add(toBeRemoved[i] = rand.NextDouble());
    		for (var i = 0; i < N; i++) avl.Add(toBeLeft[i] = rand.NextDouble());
    		for (var i = 0; i < N; i++) Console.Write(avl.Remove(toBeRemoved[i]) ? "" : "!!!NOT REMOVED!!! => " + toBeRemoved[i] + "\n");
    		var insertErrors = toBeLeft.All(x => avl.Contains(x));
    		var deleteErrors = avl.Count == N;
    		//Console.WriteLine("【AVL木の構造】");
    		//Console.WriteLine(avl);
    		if (insertErrors && deleteErrors) Console.WriteLine("○\t挿入, 削除操作が正しく行われています.");
    		else if (insertErrors) Console.WriteLine("×\t挿入(または削除)操作に問題があります.");
    		else Console.WriteLine("×\t削除(または挿入)操作に問題があります.");
    		if (avl.IsBalanced()) Console.WriteLine("○\tAVL木は平衡条件を保っています.");
    		else Console.WriteLine("×\tAVL木の平衡条件が破れています.");
    		if (avl.IsValidBinarySearchTree()) Console.WriteLine("○\tAVL木は二分探索木になっています.");
    		else Console.WriteLine("×\tAVL木は二分探索木になっていません.");
    		Array.Sort(toBeLeft, comp);
    		Console.WriteLine("最小値 : " + avl.Min() + " ≡ " + toBeLeft.First());
    		Console.WriteLine("最大値 : " + avl.Max() + " ≡ " + toBeLeft.Last());
    		Console.WriteLine("要素数 : " + avl.Count + "個");
    	}
    }
    class PriorityQueue<T> : IEnumerable<T>, ICollection, IEnumerable, ICloneable
    {
    	Comparison<T> comp;
    	List<T> list;
    	public int Count { get; private set; }
    	public bool IsEmpty { get { return Count == 0; } }
    	public PriorityQueue(IEnumerable<T> source) : this((Comparison<T>)null, 0, source) { }
    	public PriorityQueue(int capacity = 0, IEnumerable<T> source = null) : this((Comparison<T>)null, capacity, source) { }
    	public PriorityQueue(IComparer<T> comp, IEnumerable<T> source) : this(comp.ToComparison(), source) { }
    	public PriorityQueue(IComparer<T> comp, int capacity = 0, IEnumerable<T> source = null) : this(comp.ToComparison(), source) { list.Capacity = capacity; }
    	public PriorityQueue(Comparison<T> comp, IEnumerable<T> source) : this(comp, 0, source) { }
    	public PriorityQueue(Comparison<T> comp, int capacity = 0, IEnumerable<T> source = null) { this.comp = comp == null ? Func.DefaultComparison<T>() : comp; list = new List<T>(capacity); if (source != null) foreach (var x in source) Enqueue(x); }
    	/// <summary>
    	/// add an item
    	/// this is an O(log n) operation
    	/// </summary>
    	/// <param name="x">item</param>
    	public void Enqueue(T x)
    	{
    		var pos = Count++;
    		list.Add(x);
    		while (pos > 0)
    		{
    			var p = (pos - 1) / 2;
    			if (comp(list[p], x) <= 0) break;
    			list[pos] = list[p];
    			pos = p;
    		}
    		list[pos] = x;
    	}
    	/// <summary>
    	/// return the minimum element and remove it
    	/// this is an O(log n) operation
    	/// </summary>
    	/// <returns>the minimum</returns>
    	public T Dequeue()
    	{
    		var value = list[0];
    		var x = list[--Count];
    		list.RemoveAt(Count);
    		if (Count == 0) return value;
    		var pos = 0;
    		while (pos * 2 + 1 < Count)
    		{
    			var a = 2 * pos + 1;
    			var b = 2 * pos + 2;
    			if (b < Count && comp(list[b], list[a]) < 0) a = b;
    			if (comp(list[a], x) >= 0) break;
    			list[pos] = list[a];
    			pos = a;
    		}
    		list[pos] = x;
    		return value;
    	}
    	/// <summary>
    	/// look at the minimum element
    	/// this is an O(1) operation
    	/// </summary>
    	/// <returns>the minimum</returns>
    	public T Peek() { return list[0]; }
    	public IEnumerator<T> GetEnumerator() { var x = (PriorityQueue<T>)Clone(); while (x.Count > 0) yield return x.Dequeue(); }
    	void CopyTo(Array array, int index) { foreach (var x in this) array.SetValue(x, index++); }
    	public object Clone() { var x = new PriorityQueue<T>(comp, Count); x.list.AddRange(list); return x; }
    	public void Clear() { list = new List<T>(); Count = 0; }
    	public void TrimExcess() { list.TrimExcess(); }
    	/// <summary>
    	/// check whether item is in this queue
    	/// this is an O(n) operation
    	/// </summary>
    	public bool Contains(T item) { return list.Contains(item); }
    	IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
    	void ICollection.CopyTo(Array array, int index) { CopyTo(array, index); }
    	bool ICollection.IsSynchronized { get { return false; } }
    	object ICollection.SyncRoot { get { return this; } }
    }
    class Deque<T>
    {
    	T[] array;
    	int offset, capacity;
    	public int Count { get; protected set; }
    	public Deque(int capacity) { array = new T[this.capacity = capacity]; Count = 0; offset = 0; }
    	public Deque() : this(16) { }
    	public T this[int index] { get { return array[GetIndex(index)]; } set { array[GetIndex(index)] = value; } }
    	int GetIndex(int index) { var tmp = index + offset; return tmp >= capacity ? tmp - capacity : tmp; }
    	public T PeekFront() { return array[offset]; }
    	public T PeekBack() { return array[GetIndex(Count - 1)]; }
    	public void PushFront(T item)
    	{
    		if (Count == capacity) Extend();
    		if (--offset < 0) offset += array.Length;
    		array[offset] = item;
    		Count++;
    	}
    	public T PopFront()
    	{
    		Count--;
    		var tmp = array[offset++];
    		if (offset >= capacity) offset -= capacity;
    		return tmp;
    	}
    	public void PushBack(T item)
    	{
    		if (Count == capacity) Extend();
    		var id = (Count++) + offset;
    		if (id >= capacity) id -= capacity;
    		array[id] = item;
    	}
    	public T PopBack() { return array[GetIndex(--Count)]; }
    	public void Insert(int index, T item)
    	{
    		PushFront(item);
    		for (var i = 0; i < index; i++) this[i] = this[i + 1];
    		this[index] = item;
    	}
    	public T RemoveAt(int index)
    	{
    		var tmp = this[index];
    		for (var i = index; i > 0; i--) this[i] = this[i - 1];
    		PopFront();
    		return tmp;
    	}
    	void Extend()
    	{
    		var newArray = new T[capacity << 1];
    		if (offset > capacity - Count)
    		{
    			var length = array.Length - offset;
    			Array.Copy(array, offset, newArray, 0, length);
    			Array.Copy(array, 0, newArray, length, Count - length);
    		}
    		else Array.Copy(array, offset, newArray, 0, Count);
    		array = newArray;
    		offset = 0;
    		capacity <<= 1;
    	}
    }
    class PairComparer<S, T> : IComparer<Pair<S, T>>
    	where S : IComparable<S>
    	where T : IComparable<T>
    {
    	public PairComparer() { }
    	public int Compare(Pair<S, T> x, Pair<S, T> y)
    	{
    		var p = x.First.CompareTo(y.First);
    		if (p != 0) return p;
    		else return x.Second.CompareTo(y.Second);
    	}
    }
    class Pair<S, T>
    {
    	public S First;
    	public T Second;
    	public Pair() { First = default(S); Second = default(T); }
    	public Pair(S s, T t) { First = s; Second = t; }
    	public override string ToString() { return "(" + First + ", " + Second + ")"; }
    	public override int GetHashCode() { return First.GetHashCode() ^ Second.GetHashCode(); }
    	public override bool Equals(object obj)
    	{
    		if (ReferenceEquals(this, obj)) return true;
    		else if (obj == null) return false;
    		var tmp = obj as Pair<S, T>;
    		return (object)tmp != null && First.Equals(tmp.First) && Second.Equals(tmp.Second);
    	}
    }
    class Point : Pair<int, int>
    {
    	public int X { get { return First; } set { First = value; } }
    	public int Y { get { return Second; } set { Second = value; } }
    	public Point() : base(0, 0) { }
    	public Point(int x, int y) : base(x, y) { }
    	public IEnumerable<Point> Neighbors4()
    	{
    		yield return new Point(X - 1, Y);
    		yield return new Point(X, Y - 1);
    		yield return new Point(X, Y + 1);
    		yield return new Point(X + 1, Y);
    	}
    	public IEnumerable<Point> Neighbors8()
    	{
    		yield return new Point(X - 1, Y - 1);
    		yield return new Point(X - 1, Y);
    		yield return new Point(X - 1, Y + 1);
    		yield return new Point(X, Y - 1);
    		yield return new Point(X, Y + 1);
    		yield return new Point(X + 1, Y - 1);
    		yield return new Point(X + 1, Y);
    		yield return new Point(X + 1, Y + 1);
    	}
    	public static Point operator +(Point p) { return new Point(p.X, p.Y); }
    	public static Point operator -(Point p) { return new Point(-p.X, -p.Y); }
    	public static Point operator /(Point p, int r) { return new Point(p.X / r, p.Y / r); }
    	public static Point operator *(int r, Point p) { return new Point(p.X * r, p.Y * r); }
    	public static Point operator *(Point p, int r) { return new Point(p.X * r, p.Y * r); }
    	public static Point operator +(Point p, Point q) { return new Point(p.X + q.X, p.Y + q.Y); }
    	public static Point operator -(Point p, Point q) { return new Point(p.X - q.X, p.Y - q.Y); }
    }
    class Printer : IDisposable
    {
    	bool isConsole;
    	TextWriter file;
    	public Printer() { file = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false }; isConsole = true; }
    	public Printer(string path) { file = new StreamWriter(path, false) { AutoFlush = false }; isConsole = false; }
    	public void Write<T>(T value) { file.Write(value); }
    	public void Write(bool b) { file.Write(b ? "YES" : "NO"); }
    	public void Write(string str, params object[] args) { file.Write(str, args); }
    	public void WriteLine() { file.WriteLine(); }
    	public void WriteLine<T>(T value) { file.WriteLine(value); }
    	public void WriteLine(bool b) { file.WriteLine(b ? "YES" : "NO"); }
    	public void WriteLine<T>(IEnumerable<T> list) { foreach (var x in list) file.WriteLine(x); }
    	public void WriteLine<T>(List<T> list) { foreach (var x in list) file.WriteLine(x); }
    	public void WriteLine<T>(T[] list) { foreach (var x in list) file.WriteLine(x); }
    	public void WriteLine(string str, params object[] args) { file.WriteLine(str, args); }
    	public void Dispose() { file.Flush(); if (!isConsole) file.Dispose(); }
    }
    class Scanner : IDisposable
    {
    	bool isConsole;
    	TextReader file;
    	public Scanner() { file = Console.In; }
    	public Scanner(string path) { file = new StreamReader(path); isConsole = false; }
    	public void Dispose() { if (!isConsole) file.Dispose(); }
    	public T Get<T>() { return (T)Convert(file.ReadLine(), Type.GetTypeCode(typeof(T))); }
    	public int Int { get { return Get<int>(); } }
    	public uint UInt { get { return Get<uint>(); } }
    	public long Long { get { return Get<long>(); } }
    	public ulong ULong { get { return Get<ulong>(); } }
    	public double Double { get { return Get<double>(); } }
    	public decimal Decimal { get { return Get<decimal>(); } }
    	public char Char { get { return Get<char>(); } }
    	public string String { get { return Get<string>(); } }
    	public Tuple<S, T> Get<S, T>() { S s; T t; Read(out s, out t); return new Tuple<S, T>(s, t); }
    	public Tuple<S, T, U> Get<S, T, U>() { S s; T t; U u; Read(out s, out t, out u); return new Tuple<S, T, U>(s, t, u); }
    	public Tuple<S, T, U, V> Get<S, T, U, V>() { S s; T t; U u; V v; Read(out s, out t, out u, out v); return new Tuple<S, T, U, V>(s, t, u, v); }
    	public Tuple<S, T, U, V, W> Get<S, T, U, V, W>() { S s; T t; U u; V v; W w; Read(out s, out t, out u, out v, out w); return new Tuple<S, T, U, V, W>(s, t, u, v, w); }
    	public Tuple<S, T, U, V, W, X> Get<S, T, U, V, W, X>() { S s; T t; U u; V v; W w; X x; Read(out s, out t, out u, out v, out w, out x); return new Tuple<S, T, U, V, W, X>(s, t, u, v, w, x); }
    	public Tuple<S, T, U, V, W, X, Y> Get<S, T, U, V, W, X, Y>() { S s; T t; U u; V v; W w; X x; Y y; Read(out s, out t, out u, out v, out w, out x, out y); return new Tuple<S, T, U, V, W, X, Y>(s, t, u, v, w, x, y); }
    	public Tuple<S, T, U, V, W, X, Y, Z> Get<S, T, U, V, W, X, Y, Z>() { S s; T t; U u; V v; W w; X x; Y y; Z z; Read(out s, out t, out u, out v, out w, out x, out y, out z); return new Tuple<S, T, U, V, W, X, Y, Z>(s, t, u, v, w, x, y, z); }
    	public Pair<S, T> Pair<S, T>() { S s; T t; Read(out s, out t); return new Pair<S, T>(s, t); }
    	object Convert(string str, TypeCode type)
    	{
    		if (type == TypeCode.Int32) return int.Parse(str);
    		else if (type == TypeCode.UInt32) return uint.Parse(str);
    		else if (type == TypeCode.Int64) return long.Parse(str);
    		else if (type == TypeCode.UInt64) return ulong.Parse(str);
    		else if (type == TypeCode.Double) return double.Parse(str);
    		else if (type == TypeCode.Decimal) return decimal.Parse(str);
    		else if (type == TypeCode.Char) return str[0];
    		else if (type == TypeCode.String) return str;
    		else if (type == Type.GetTypeCode(typeof(Point))) { int s, t; Read(out s, out t); return new Point(s, t); }
    		else throw new Exception();
    	}
    	public T[] ReadMany<T>() { var type = Type.GetTypeCode(typeof(T)); return file.ReadLine().Split(sep, StringSplitOptions.RemoveEmptyEntries).Select(str => (T)Convert(str, type)).ToArray(); }
    	public T[] ReadMany<T>(int n) { var type = Type.GetTypeCode(typeof(T)); return file.ReadLine().Split(sep, StringSplitOptions.RemoveEmptyEntries).Take(n).Select(str => (T)Convert(str, type)).ToArray(); }
    	public T[] ReadManyLines<T>(int n, Func<T> selector) { return Enumerable.Range(0, n).Select(_ => selector()).ToArray(); }
    	public T[] ReadManyLines<T>(int n) { return Enumerable.Range(0, n).Select(_ => Get<T>()).ToArray(); }
    	public Tuple<S, T>[] ReadManyLines<S, T>(int n) { return Enumerable.Range(0, n).Select(_ => Get<S, T>()).ToArray(); }
    	public Tuple<S, T, U>[] ReadManyLines<S, T, U>(int n) { return Enumerable.Range(0, n).Select(_ => Get<S, T, U>()).ToArray(); }
    	public Tuple<S, T, U, V>[] ReadManyLines<S, T, U, V>(int n) { return Enumerable.Range(0, n).Select(_ => Get<S, T, U, V>()).ToArray(); }
    	public Tuple<S, T, U, V, W>[] ReadManyLines<S, T, U, V, W>(int n) { return Enumerable.Range(0, n).Select(_ => Get<S, T, U, V, W>()).ToArray(); }
    	public Tuple<S, T, U, V, W, X>[] ReadManyLines<S, T, U, V, W, X>(int n) { return Enumerable.Range(0, n).Select(_ => Get<S, T, U, V, W, X>()).ToArray(); }
    	public Tuple<S, T, U, V, W, X, Y>[] ReadManyLines<S, T, U, V, W, X, Y>(int n) { return Enumerable.Range(0, n).Select(_ => Get<S, T, U, V, W, X, Y>()).ToArray(); }
    	public Tuple<S, T, U, V, W, X, Y, Z>[] ReadManyLines<S, T, U, V, W, X, Y, Z>(int n) { return Enumerable.Range(0, n).Select(_ => Get<S, T, U, V, W, X, Y, Z>()).ToArray(); }
    	public T[,] ReadManyManyLines<T>(int X, int Y)
    	{
    		var array = new T[X, Y];
    		for (var y = 0; y < Y; y++) { var tmp = ReadMany<T>(X); for (var x = 0; x < X; x++) array[x, y] = tmp[x]; }
    		return array;
    	}
    	public void Read<S>(out S s)
    	{
    		var read = ReadMulti(Type.GetTypeCode(typeof(S))).ToArray();
    		s = (S)read[0];
    	}
    	public void Read<S, T>(out S s, out T t)
    	{
    		var read = ReadMulti(Type.GetTypeCode(typeof(S)), Type.GetTypeCode(typeof(T))).ToArray();
    		s = (S)read[0];
    		t = (T)read[1];
    	}
    	public void Read<S, T, U>(out S s, out T t, out U u)
    	{
    		var read = ReadMulti(Type.GetTypeCode(typeof(S)), Type.GetTypeCode(typeof(T)), Type.GetTypeCode(typeof(U))).ToArray();
    		s = (S)read[0];
    		t = (T)read[1];
    		u = (U)read[2];
    	}
    	public void Read<S, T, U, V>(out S s, out T t, out U u, out V v)
    	{
    		var read = ReadMulti(Type.GetTypeCode(typeof(S)), Type.GetTypeCode(typeof(T)), Type.GetTypeCode(typeof(U)), Type.GetTypeCode(typeof(V))).ToArray();
    		s = (S)read[0];
    		t = (T)read[1];
    		u = (U)read[2];
    		v = (V)read[3];
    	}
    	public void Read<S, T, U, V, W>(out S s, out T t, out U u, out V v, out W w)
    	{
    		var read = ReadMulti(Type.GetTypeCode(typeof(S)), Type.GetTypeCode(typeof(T)),
    			Type.GetTypeCode(typeof(U)), Type.GetTypeCode(typeof(V)), Type.GetTypeCode(typeof(W))).ToArray();
    		s = (S)read[0];
    		t = (T)read[1];
    		u = (U)read[2];
    		v = (V)read[3];
    		w = (W)read[4];
    	}
    	public void Read<S, T, U, V, W, X>(out S s, out T t, out U u, out V v, out W w, out X x)
    	{
    		var read = ReadMulti(Type.GetTypeCode(typeof(S)), Type.GetTypeCode(typeof(T)),
    			Type.GetTypeCode(typeof(U)), Type.GetTypeCode(typeof(V)), Type.GetTypeCode(typeof(W)), Type.GetTypeCode(typeof(X))).ToArray();
    		s = (S)read[0];
    		t = (T)read[1];
    		u = (U)read[2];
    		v = (V)read[3];
    		w = (W)read[4];
    		x = (X)read[5];
    	}
    	public void Read<S, T, U, V, W, X, Y>(out S s, out T t, out U u, out V v, out W w, out X x, out Y y)
    	{
    		var read = ReadMulti(Type.GetTypeCode(typeof(S)), Type.GetTypeCode(typeof(T)),
    			Type.GetTypeCode(typeof(U)), Type.GetTypeCode(typeof(V)), Type.GetTypeCode(typeof(W)), Type.GetTypeCode(typeof(X)), Type.GetTypeCode(typeof(Y))).ToArray();
    		s = (S)read[0];
    		t = (T)read[1];
    		u = (U)read[2];
    		v = (V)read[3];
    		w = (W)read[4];
    		x = (X)read[5];
    		y = (Y)read[6];
    	}
    	public void Read<S, T, U, V, W, X, Y, Z>(out S s, out T t, out U u, out V v, out W w, out X x, out Y y, out Z z)
    	{
    		var read = ReadMulti(Type.GetTypeCode(typeof(S)), Type.GetTypeCode(typeof(T)),
    			Type.GetTypeCode(typeof(U)), Type.GetTypeCode(typeof(V)), Type.GetTypeCode(typeof(W)),
    			Type.GetTypeCode(typeof(X)), Type.GetTypeCode(typeof(Y)), Type.GetTypeCode(typeof(Z))).ToArray();
    		s = (S)read[0];
    		t = (T)read[1];
    		u = (U)read[2];
    		v = (V)read[3];
    		w = (W)read[4];
    		x = (X)read[5];
    		y = (Y)read[6];
    		z = (Z)read[7];
    	}
    	static char[] sep = new char[] { ' ', '/' };
    	IEnumerable<object> ReadMulti(params TypeCode[] types)
    	{
    		var input = file.ReadLine().Split(sep, StringSplitOptions.RemoveEmptyEntries);
    		for (var i = 0; i < types.Length; i++) yield return Convert(input[i], types[i]);
    	}
    	public T[,] Board<T>(int X, int Y, Func<char, int, int, T> selector)
    	{
    		var array = new T[X, Y];
    		for (var y = 0; y < Y; y++)
    		{
    			var str = Get<string>();
    			for (var x = 0; x < X; x++) array[x, y] = selector(str[x], x, y);
    		}
    		return array;
    	}
    }
    static class Func
    {
    	public const int Inf = 1073741789;  // 2 * Inf < int.MaxValue, and Inf is a prime number
    	public const long InfL = 4011686018427387913L;  // 2 * InfL < long.MaxValue, and InfL is a prime number
    	public static Comparison<T> DefaultComparison<T>() { return (x, y) => Comparer<T>.Default.Compare(x, y); }
    	public static Comparison<T> ToComparison<T>(this IComparer<T> comp) { return comp == null ? DefaultComparison<T>() : (x, y) => comp.Compare(x, y); }
    	/// <summary>
    	/// Find the first number x such that pred(x) is true
    	/// if pred(x) is false for all min&lt;=x&lt;max, then return max
    	/// in other words, pred(max) is assumed to be true
    	/// </summary>
    	/// <param name="min">inclusive lower limit</param>
    	/// <param name="max">exclusive upper limit</param>
    	/// <param name="pred">monotonous predicate, i.e. if pred(a) and a&lt;b, then pred(b)</param>
    	/// <returns>first number such that satisfy pred</returns>
    	public static long FirstBinary(long min, long max, Predicate<long> pred)
    	{
    		while (min < max)
    		{
    			var mid = (min + max) / 2;
    			if (pred(mid)) max = mid;
    			else min = mid + 1;
    		}
    		return min;
    	}
    	/// <summary>
    	/// Find the first number x such that pred(x) is true
    	/// if pred(x) is false for all min&lt;=x&lt;max, then return max
    	/// in other words, pred(max) is assumed to be true
    	/// </summary>
    	/// <param name="min">inclusive lower limit</param>
    	/// <param name="max">exclusive upper limit</param>
    	/// <param name="pred">monotonous predicate, i.e. if pred(a) and a&lt;b, then pred(b)</param>
    	/// <returns>first number such that satisfy pred</returns>
    	public static int FirstBinary(int min, int max, Predicate<int> pred)
    	{
    		while (min < max)
    		{
    			var mid = (min + max) / 2;
    			if (pred(mid)) max = mid;
    			else min = mid + 1;
    		}
    		return min;
    	}
    	public static Dictionary<T, S> Reverse<S, T>(this IDictionary<S, T> dict)
    	{
    		var r = new Dictionary<T, S>();
    		foreach (var t in dict) r.Add(t.Value, t.Key);
    		return r;
    	}
    	public static void Swap<T>(this IList<T> array, int i, int j) { var tmp = array[i]; array[i] = array[j]; array[j] = tmp; }
    	public static void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    	public static T IndexAt<T>(this T[,] array, Pair<int, int> index) { return array[index.First, index.Second]; }
    	public static bool InRegion(this Pair<int, int> p, int X, int Y) { return p.InRegion(0, X, 0, Y); }
    	public static bool InRegion(this Pair<int, int> p, int x, int X, int y, int Y) { return p.First >= x && p.Second >= y && p.First < X && p.Second < Y; }
    	/// <summary>
    	/// get all permutation of 0, 1, ..., n - 1
    	/// </summary>
    	/// <param name="n">length of array</param>
    	/// <param name="func">if you want to change the elements of the array, you must take a copy</param>
    	public static void Permutation(int n, Action<int[]> func)
    	{
    		var array = new int[n];
    		var unused = new bool[n];
    		for (var i = 0; i < n; i++) unused[i] = true;
    		Permutation(n, 0, array, unused, func);
    	}
    	static void Permutation(int n, int i, int[] array, bool[] unused, Action<int[]> func)
    	{
    		if (i == n) func(array);
    		else
    			for (var x = 0; x < n; x++)
    				if (unused[x])
    				{
    					array[i] = x;
    					unused[x] = false;
    					Permutation(n, i + 1, array, unused, func);
    					unused[x] = true;
    				}
    	}
    	public static long Fact(int n)
    	{
    		var fact = 1L;
    		for (var i = 2; i <= n; i++) fact *= i;
    		return fact;
    	}
    	public static Dictionary<long, int> Factorize(this long n, List<int> primes)
    	{
    		var d = new Dictionary<long, int>();
    		for (var j = 0; j < primes.Count; j++)
    		{
    			var i = primes[j];
    			if (i * i > n) break;
    			if (n % i == 0)
    			{
    				d.Add(i, 0);
    				while (n % i == 0) { n /= i; d[i]++; }
    			}
    		}
    		if (n > 1) d.Add(n, 1);
    		return d;
    	}
    	public static Dictionary<long, int> Factorize(this long n)
    	{
    		var d = new Dictionary<long, int>();
    		for (var i = 2L; i * i <= n; i++)
    			if (n % i == 0)
    			{
    				d.Add(i, 0);
    				while (n % i == 0) { n /= i; d[i]++; }
    			}
    		if (n > 1) d.Add(n, 1);
    		return d;
    	}
    	public static long LCM(long n, long m) { return Math.Abs((n / GCD(n, m)) * m); }
    	public static long Divide(long n, long m) { return (n - Remainder(n, m)) / m; }
    	public static long Remainder(long n, long m)
    	{
    		if (m == 0) throw new DivideByZeroException();
    		else if (m < 0) return Remainder(n, -m);
    		else
    		{
    			var r = n % m;
    			return r < 0 ? r + m : r;
    		}
    	}
    	public static long Recurrence(long[] coeff, long[] init, long N, long mod)
    	{
    		var K = init.Length;
    		if (N < 0)
    		{
    			var inv = Inverse(coeff[0], mod);
    			var rc = new long[K];
    			for (var i = 1; i < K; i++) rc[K - i] = -coeff[i] * inv % mod;
    			rc[0] = inv;
    			var ri = new long[K];
    			for (var i = 0; i < K; i++) ri[K - 1 - i] = init[i];
    			return Recurrence(rc, ri, K - 1 - N, mod);
    		}
    		var tmp = new long[K];
    		Recurrence(coeff, init, tmp, N, mod);
    		var sum = 0L;
    		for (var i = 0; i < K; i++) sum += init[i] * tmp[i] % mod;
    		sum %= mod;
    		if (sum < 0) sum += mod;
    		return sum;
    	}
    	public static void Recurrence(long[] coeff, long[] init, long[] state, long N, long mod)
    	{
    		var K = init.Length;
    		if (N < K) state[N] = init[N];
    		else if ((N & 1) == 0)
    		{
    			var tmp = new long[K][];
    			for (var i = 0; i < K; i++) tmp[i] = new long[K];
    			Recurrence(coeff, init, tmp[0], N / 2, mod);
    			for (var i = 1; i < K; i++) tmp[i] = Next(coeff, tmp[i - 1], mod);
    			for (var i = 0; i < K; i++)
    			{
    				state[i] = 0;
    				for (var j = 0; j < K; j++) state[i] += tmp[0][j] * tmp[j][i] % mod;
    				state[i] %= mod;
    			}
    		}
    		else if (N < 2 * K || (N & 2) == 0)
    		{
    			var tmp = new long[K];
    			Recurrence(coeff, init, tmp, N - 1, mod);
    			tmp = Next(coeff, tmp, mod);
    			for (var i = 0; i < K; i++) state[i] = tmp[i];
    		}
    		else
    		{
    			var tmp = new long[K];
    			Recurrence(coeff, init, tmp, N + 1, mod);
    			tmp = Prev(coeff, tmp, mod);
    			for (var i = 0; i < K; i++) state[i] = tmp[i];
    		}
    	}
    	static long[] Next(long[] coeff, long[] state, long mod)
    	{
    		var K = coeff.Length;
    		var tmp = new long[K];
    		for (var i = 0; i < K; i++) tmp[i] = coeff[i] * state[K - 1] % mod;
    		for (var i = 1; i < K; i++) tmp[i] = (tmp[i] + state[i - 1]) % mod;
    		return tmp;
    	}
    	static long[] Prev(long[] coeff, long[] state, long mod)
    	{
    		var K = coeff.Length;
    		var tmp = new long[K];
    		var inv = Inverse(coeff[0], mod);
    		tmp[K - 1] = state[0] * inv % mod;
    		for (var i = 1; i < K; i++) tmp[i - 1] = (state[i] - coeff[i] * tmp[K - 1] % mod) % mod;
    		return tmp;
    	}
    	// get all primes less than or equal to n
    	public static List<int> GetPrimes(int n)
    	{
    		if (n < 3) n = 3;
    		var m = (n - 1) >> 1;
    		var primes = new List<int>((int)(n / Math.Log(n)));
    		primes.Add(2);
    		var composites = new bool[m];
    		composites[0] = false;
    		for (var p = 0; p < m; p++)
    		{
    			if (!composites[p])
    			{
    				var pnum = 2 * p + 3;
    				primes.Add(pnum);
    				for (var k = 3 * p + 3; k < m; k += pnum) composites[k] = true;
    			}
    		}
    		return primes;
    	}
    	/// <summary>
    	/// solve nx+my=1 and returns (x,y)
    	/// </summary>
    	/// <param name="n">assumed to be with m</param>
    	/// <param name="m">assumed to be with n</param>
    	/// <returns>(x,y) where nx+my=1</returns>
    	public static Tuple<long, long> SolveLinear(long n, long m)
    	{
    		if (n < 0) { var p = SolveLinear(-n, m); return p == null ? p : new Tuple<long, long>(-p.Item1, p.Item2); }
    		if (m < 0) { var p = SolveLinear(n, -m); return p == null ? p : new Tuple<long, long>(p.Item1, -p.Item2); }
    		if (n < m) { var p = SolveLinear(m, n); return p == null ? p : new Tuple<long, long>(p.Item2, p.Item1); }
    		long a = 1, b = 0, c = 0, d = 1;
    		while (m > 0)
    		{
    			var r = n % m;
    			var q = n / m;
    			n = m;
    			m = r;
    			var tmp = a;
    			a = -a * q + b;
    			b = tmp;
    			tmp = c;
    			c = -c * q + d;
    			d = tmp;
    		}
    		return n != 1 ? null : new Tuple<long, long>(d, b);
    	}
    	public static int GCD(int n, int m)
    	{
    		var a = Math.Abs(n);
    		var b = Math.Abs(m);
    		if (a < b) { var c = a; a = b; b = c; }
    		while (b > 0)
    		{
    			var c = a % b;
    			a = b;
    			b = c;
    		}
    		return a;
    	}
    	/*public static long GCD(long n, long m)
    	{
    		var a = Math.Abs(n);
    		var b = Math.Abs(m);
    		if (a < b) { var c = a; a = b; b = c; }
    		while (b > 0)
    		{
    			var c = a % b;
    			a = b;
    			b = c;
    		}
    		return a;
    	}*/
    	public static long GCD(long a, long b)
    	{
    		var n = (ulong)Math.Abs(a); var m = (ulong)Math.Abs(b);
    		if (n == 0) return (long)m; if (m == 0) return (long)n;
    		int zm = 0, zn = 0;
    		while ((n & 1) == 0) { n >>= 1; zn++; }
    		while ((m & 1) == 0) { m >>= 1; zm++; }
    		while (m != n)
    		{
    			if (m > n) { m -= n; while ((m & 1) == 0) m >>= 1; }
    			else { n -= m; while ((n & 1) == 0) n >>= 1; }
    		}
    		return (long)n << Math.Min(zm, zn);
    	}
    	public static BigInteger GCD(BigInteger a, BigInteger b) { return BigInteger.GreatestCommonDivisor(a, b); }
    	public static long Inverse(long a, long mod)
    	{
    		if (a < 0) { a %= mod; if (a < 0) a += mod; }
    		var t = SolveLinear(a, mod);
    		return t.Item1 > 0 ? t.Item1 : t.Item1 + mod;
    	}
    	public static ulong Pow(ulong a, ulong b, ulong mod)
    	{
    		var p = 1uL;
    		var x = a;
    		while (b > 0)
    		{
    			if ((b & 1) == 1) p = (p * x) % mod;
    			b >>= 1;
    			x = (x * x) % mod;
    		}
    		return p;
    	}
    	public static long Pow(long a, long b, long mod)
    	{
    		var p = 1L;
    		var x = a;
    		while (b > 0)
    		{
    			if ((b & 1) == 1) p = (p * x) % mod;
    			b >>= 1;
    			x = (x * x) % mod;
    		}
    		return p;
    	}
    	public static long Pow(long a, long b)
    	{
    		if (a == 1) return 1;
    		else if (a == 0) { if (b >= 0) return 0; else throw new DivideByZeroException(); }
    		else if (b < 0) return 0;
    		var p = 1l;
    		var x = a;
    		while (b > 0)
    		{
    			if ((b & 1) == 1) p *= x;
    			b >>= 1;
    			x *= x;
    		}
    		return p;
    	}
    	public static ulong Pow(ulong a, ulong b)
    	{
    		var p = 1ul;
    		var x = a;
    		while (b > 0)
    		{
    			if ((b & 1) == 1) p *= x;
    			b >>= 1;
    			x *= x;
    		}
    		return p;
    	}
    	public static long ChineseRemainder(Tuple<long, long> modRemainder1, Tuple<long, long> modRemainder2)
    	{
    		var m1 = modRemainder1.Item1;
    		var m2 = modRemainder2.Item1;
    		var a1 = modRemainder1.Item2;
    		var a2 = modRemainder2.Item2;
    		var t = SolveLinear(m1, m2);
    		var n1 = t.Item1;
    		var n2 = t.Item2;
    		return (m1 * n1 * a2 + m2 * n2 * a1) % (m1 * m2);
    	}
    	public static long ChineseRemainder(params Tuple<long, long>[] modRemainder)
    	{
    		if (modRemainder.Length == 0) throw new DivideByZeroException();
    		else if (modRemainder.Length == 1) return modRemainder[0].Item2;
    		else if (modRemainder.Length == 2) return ChineseRemainder(modRemainder[0], modRemainder[1]);
    		else
    		{
    			var tuple = new Tuple<long, long>(1, 0);
    			for (var i = 0; i < modRemainder.Length; i++)
    			{
    				var tmp = ChineseRemainder(tuple, modRemainder[i]);
    				tuple = new Tuple<long, long>(tuple.Item1 * modRemainder[i].Item1, tmp);
    			}
    			return tuple.Item2;
    		}
    	}
    	// forward transform -> theta= 2*PI/n
    	// reverse transform -> theta=-2*PI/n, and use a[i]/n instead of a
    	// O(n*log(n))
    	public static void FastFourierTransform(int n, double theta, Complex[] a)
    	{
    		for (var m = n; m >= 2; m >>= 1)
    		{
    			var mh = m >> 1;
    			for (var i = 0; i < mh; i++)
    			{
    				var w = Complex.Exp(i * theta * Complex.ImaginaryOne);
    				for (var j = i; j < n; j += m)
    				{
    					var k = j + mh;
    					var x = a[j] - a[k];
    					a[j] += a[k];
    					a[k] = w * x;
    				}
    			}
    			theta *= 2;
    		}
    		var s = 0;
    		for (var j = 1; j < n - 1; j++)
    		{
    			for (var k = n >> 1; k > (s ^= k); k >>= 1) ;
    			if (j < s) a.Swap(s, j);
    		}
    	}
    	// get table of Euler function
    	// let return value f, f[i]=phi(i) for 0<=i<=n
    	// nearly O(n)
    	public static long[] EulerFunctionTable(long n)
    	{
    		if (n < 2) n = 2;
    		var f = new long[n + 1];
    		for (var i = 0L; i <= n; i++) f[i] = i;
    		for (var i = 2L; i <= n; i++) if (f[i] == i) for (var j = i; j <= n; j += i) f[j] = f[j] / i * (i - 1);
    		return f;
    	}
    	// O(sqrt(n))
    	public static long EulerFunction(long n)
    	{
    		var res = n;
    		for (var i = 2L; i * i <= n; i++)
    			if (n % i == 0)
    			{
    				res = res / i * (i - 1);
    				do n /= i; while (n % i == 0);
    			}
    		if (n != 1) res = res / n * (n - 1);
    		return res;
    	}
    	// get moebius function of d s.t. 0<=d<=n
    	// O(n)
    	public static int[] MoebiusFunctionTable(long n)
    	{
    		if (n < 2) n = 2;
    		var f = new int[n + 1];
    		var p = new bool[n + 1];
    		for (var i = 0L; i <= n; i++) f[i] = 1;
    		for (var i = 2L; i <= n; i++) if (!p[i])
    			{
    				for (var j = i; j <= n; j += i) { f[j] *= -1; p[j] = true; }
    				for (var j = i * i; j <= n; j += i * i) f[j] = 0;
    			}
    		return f;
    	}
    	// get moebius function of d s.t. d|n
    	// if dict.ContainsKey(d), dict[d]!=0, otherwise moebius function of d is 0
    	// O(sqrt(n))
    	public static Dictionary<long, int> MoebiusFunctionOfDivisors(long n)
    	{
    		var ps = new List<long>();
    		for (var i = 2L; i * i <= n; i++)
    			if (n % i == 0)
    			{
    				ps.Add(i);
    				do n /= i; while (n % i == 0);
    			}
    		if (n != 1) ps.Add(n);
    		var dict = new Dictionary<long, int>();
    		var m = ps.Count;
    		for (var i = 0; i < (1 << m); i++)
    		{
    			var mu = 1;
    			var k = 1L;
    			for (var j = 0; j < m; j++) if ((i & (1 << j)) != 0) { mu *= -1; k *= ps[j]; }
    			dict.Add(k, mu);
    		}
    		return dict;
    	}
    	// O(sqrt(n))
    	public static int MoebiusFunction(long n)
    	{
    		var mu = 1;
    		for (var i = 2L; i * i <= n; i++)
    			if (n % i == 0)
    			{
    				mu *= -1;
    				if ((n /= i) % i == 0) return 0;
    			}
    		return n == 1 ? mu : -mu;
    	}
    	// O(sqrt(n))
    	public static long CarmichaelFunction(long n)
    	{
    		var lambda = 1L;
    		var c = 0;
    		while (n % 2 == 0) { n /= 2; c++; }
    		if (c == 2) lambda = 2; else if (c > 2) lambda = 1 << (c - 2);
    		for (var i = 3L; i * i <= n; i++)
    			if (n % i == 0)
    			{
    				var tmp = i - 1;
    				n /= i;
    				while (n % i == 0) { n /= i; tmp *= i; }
    				lambda = LCM(lambda, tmp);
    			}
    		if (n != 1) lambda = LCM(lambda, n - 1);
    		return lambda;
    	}
    	// a+bi is Gaussian prime or not
    	public static bool IsGaussianPrime(ulong a, ulong b)
    	{
    		if (a == 0) return b % 4 == 3 && IsPrime(b);
    		else if (b == 0) return a % 4 == 3 && IsPrime(a);
    		else return IsPrime(a * a + b * b);
    	}
    	// nearly O(200)
    	public static bool IsPrime(ulong n)
    	{
    		if (n <= 1 || (n > 2 && n % 2 == 0)) return false;
    		var test = new uint[] { 2, 3, 5, 7, 11, 13, 17, 19, 23, 111 };
    		var d = n - 1;
    		int s = 0;
    		while (d % 2 == 0) { ++s; d /= 2; }
    		Predicate<ulong> f = t =>
    		{
    			var x = Pow(t, d, n);
    			if (x == 1) return true;
    			for (var r = 0L; r < s; r++)
    			{
    				if (x == n - 1) return true;
    				x = (x * x) % n;
    			}
    			return false;
    		};
    		for (var i = 0; test[i] < n && test[i] != 111; i++) if (!f(test[i])) return false;
    		return true;
    	}
    	public static decimal MeasureTime(Action action)
    	{
    		var sw = new System.Diagnostics.Stopwatch();
    		sw.Restart();
    		action();
    		sw.Stop();
    		return sw.ElapsedTicks * 1000m / System.Diagnostics.Stopwatch.Frequency;
    	}
    	static readonly double GoldenRatio = 2 / (3 + Math.Sqrt(5));
    	// assume f is 凹
    	// find c s.t. a<=c<=b and for all a<=x<=b, f(c)<=f(x)
    	public static double GoldenSectionSearch(double a, double b, Func<double, double> f)
    	{
    		double c = a + GoldenRatio * (b - a), d = b - GoldenRatio * (b - a);
    		double fc = f(c), fd = f(d);
    		while (d - c > 1e-9)
    		{
    			if (fc > fd)
    			{
    				a = c; c = d; d = b - GoldenRatio * (b - a);
    				fc = fd; fd = f(d);
    			}
    			else
    			{
    				b = d; d = c; c = a + GoldenRatio * (b - a);
    				fd = fc; fc = f(c);
    			}
    		}
    		return c;
    	}
    	// O(NW)
    	public static int KnapsackW(int[] w, int[] v, int W)
    	{
    		var N = w.Length;
    		var dp = new int[W + 1];
    		for (var i = 0; i < N; i++) for (var j = W; j >= w[i]; j--)
    				dp[j] = Math.Max(dp[j], v[i] + dp[j - w[i]]);
    		return dp[W];
    	}
    	// O(NV)
    	public static int KnapsackV(int[] w, int[] v, int W)
    	{
    		var N = w.Length;
    		var V = v.Sum();
    		var dp = new int[V + 1];
    		for (var i = 1; i <= V; i++) dp[i] = Inf;
    		for (var i = 0; i < N; i++) for (var j = V; j >= v[i]; j--)
    				dp[j] = Math.Min(dp[j], w[i] + dp[j - v[i]]);
    		for (var j = V; j >= 0; j--) if (dp[j] <= W) return j;
    		return 0;
    	}
    	// O(N*2^(N/2))
    	public static long KnapsackN(long[] w, long[] v, int W)
    	{
    		var N = w.Length;
    		var half = N / 2;
    		var items = new Tuple<long, long>[N];
    		for (var i = 0; i < N; i++) items[i] = new Tuple<long, long>(w[i], v[i]);
    		Array.Sort(items, (x, y) => x.Item1.CompareTo(y.Item1));
    		Func<int, int, List<Pair<long, long>>> gen = (start, end) =>
    		{
    			if (start >= end) return new List<Pair<long, long>>();
    			var lim = 1 << (end - start);
    			var list = new List<Pair<long, long>>();
    			for (var i = 0; i < lim; i++)
    			{
    				var weight = 0L;
    				var value = 0L;
    				var tmp = i;
    				for (var j = start; j < end; j++)
    				{
    					if ((tmp & 1) == 1) { weight += items[j].Item1; value += items[j].Item2; }
    					tmp >>= 1;
    				}
    				if (weight <= W) list.Add(new Pair<long, long>(weight, value));
    			}
    			list.Sort((x, y) => { var c = x.First.CompareTo(y.First); return c == 0 ? x.Second.CompareTo(y.Second) : c; });
    			var n = list.Count;
    			if (n == 0) return list;
    			for (var i = list.Count - 2; i >= 0; i--) if (list[i].First == list[i + 1].First) list[i].Second = Math.Max(list[i].Second, list[i + 1].Second);
    			var small = new List<Pair<long, long>>();
    			var last = -1;
    			while (last + 1 < n)
    			{
    				var tmp = list[last + 1].First;
    				last = Func.FirstBinary(last + 1, n, x => list[x].First > tmp) - 1;
    				if (small.Count == 0 || list[last].Second > small[small.Count - 1].Second) small.Add(list[last]);
    			}
    			return small;
    		};
    		var first = gen(0, half);
    		var second = gen(half, N);
    		var max = 0L;
    		var last2 = second.Count;
    		foreach (var item in first)
    		{
    			last2 = Func.FirstBinary(0, last2, x => second[x].First > W - item.First) - 1;
    			if (last2 < 0) break;
    			if (second[last2].First <= W - item.First) Func.SetToMax(ref max, item.Second + second[last2].Second);
    			last2++;
    		}
    		return max;
    	}
    	// nums[i] が counts[i] 個
    	// K is partial sum?
    	// O(NK)
    	public static bool PartialSum(int[] nums, int[] counts, int K)
    	{
    		var N = nums.Length;
    		var memo = new int[K + 1];
    		for (var s = 1; s <= K; s++) memo[s] = -1;
    		for (var n = 0; n < N; n++) for (var s = 0; s <= K; s++) memo[s] = memo[s] >= 0 ? counts[n] : s < nums[n] ? -1 : memo[s - nums[n]] - 1;
    		return memo[K] >= 0;
    	}
    	// O(N log(N))
    	public static int LongestIncreasingSubsequence(int[] a)
    	{
    		var N = a.Length;
    		var memo = new int[N];
    		for (var n = 0; n < N; n++) memo[n] = Inf;
    		for (var n = 0; n < N; n++)
    		{
    			var k = Func.FirstBinary(0, N, x => a[n] <= memo[x]);
    			memo[k] = a[n];
    		}
    		return Func.FirstBinary(0, N, x => memo[x] == Inf);
    	}
    	// O(nm)
    	public static int LongestCommonSubsequence(string s, string t)
    	{
    		var n = s.Length;
    		var m = t.Length;
    		var memo = new int[n + 1, m + 1];
    		for (int i = n - 1; i >= 0; i--)
    			for (int j = m - 1; j >= 0; j--)
    				if (s[i] == t[j]) memo[i, j] = memo[i + 1, j + 1] + 1;
    				else memo[i, j] = Math.Max(memo[i + 1, j], memo[i, j + 1]);
    		return memo[0, 0];
    	}
    	// the number of ways of dividing N to M numbers
    	// O(NM)
    	public static int Partition(int N, int M, int Mod)
    	{
    		var memo = new long[N + 1, M + 1];
    		for (var m = 0; m <= M; m++) memo[0, m] = 1;
    		for (var n = 1; n <= N; n++)
    		{
    			memo[n, 0] = 0;
    			for (var m = 1; m <= M; m++) memo[n, m] = (memo[n, m - 1] + (n - m >= 0 ? memo[n - m, m] : 0)) % Mod;
    		}
    		return (int)memo[N, M];
    	}
    	// max{f(a)+...+f(b-1) | from<=a<b<=to}
    	// O(to-from)
    	public static long MaxIntervalSum(int from, int to, Func<long, long> f)
    	{
    		long max, dp;
    		max = dp = f(from);
    		for (var i = from + 1; i < to; i++)
    		{
    			var tmp = f(i);
    			dp = tmp + Math.Max(0, dp);
    			max = Math.Max(max, dp);
    		}
    		return max;
    	}
    	public static int MaxElement<T>(this IEnumerable<T> source, Comparison<T> comp)
    	{
    		var p = source.GetEnumerator();
    		if (!p.MoveNext()) return -1;
    		var max = p.Current;
    		var mi = 0;
    		var i = 0;
    		while (p.MoveNext())
    		{
    			i++;
    			if (comp(max, p.Current) < 0)
    			{
    				max = p.Current;
    				mi = i;
    			}
    		}
    		return mi;
    	}
    	public static int MaxElement<T>(this IEnumerable<T> source) where T : IComparable<T> { return source.MaxElement((x, y) => x.CompareTo(y)); }
    	public static int MinElement<T>(IEnumerable<T> source, Comparison<T> comp) { return source.MaxElement((x, y) => comp(y, x)); }
    	public static int MinElement<T>(IEnumerable<T> source) where T : IComparable<T> { return source.MaxElement((x, y) => y.CompareTo(x)); }
    	public static void Shuffle<T>(IList<T> source, Random rand) { for (var i = source.Count - 1; i >= 0; --i) source.Swap(i, rand.Next(0, i + 1)); }
    	public static void Shuffle<T>(IList<T> source, RandomSFMT rand) { for (var i = source.Count - 1; i >= 0; --i) source.Swap(i, rand.Next(0, i + 1)); }
    	public static char NextChar(this Random rand) { return (char)(rand.Next(0, 'z' - 'a' + 1) + 'a'); }
    	public static char NextChar(this RandomSFMT rand) { return (char)(rand.Next(0, 'z' - 'a' + 1) + 'a'); }
    	public static string NextString(this Random rand, int length) { return new string(Enumerable.Range(0, length).Select(_ => rand.NextChar()).ToArray()); }
    	public static string NextString(this RandomSFMT rand, int length) { return new string(Enumerable.Range(0, length).Select(_ => rand.NextChar()).ToArray()); }
    	public static IEnumerable<T> Rotate<T>(this IEnumerable<T> source)
    	{
    		var e = source.GetEnumerator();
    		if (e.MoveNext())
    		{
    			var f = e.Current;
    			while (e.MoveNext()) yield return e.Current;
    			yield return f;
    		}
    	}
    	public static T Apply<T>(this Func<T, T> func, T x, int n)
    	{
    		var a = x;
    		for (var i = 0; i < n; i++) a = func(a);
    		return a;
    	}
    	public static void MemberSet<T>(this T[] array, T value)
    	{
    		var X = array.Length;
    		for (var x = 0; x < X; x++) array[x] = value;
    	}
    	public static void MemberSet<T>(this T[,] array, T value)
    	{
    		var X = array.GetLength(0); var Y = array.GetLength(1);
    		for (var x = 0; x < X; x++) for (var y = 0; y < Y; y++) array[x, y] = value;
    	}
    	public static void MemberSet<T>(this T[,,] array, T value)
    	{
    		var X = array.GetLength(0); var Y = array.GetLength(1); var Z = array.GetLength(2);
    		for (var x = 0; x < X; x++) for (var y = 0; y < Y; y++) for (var z = 0; z < Z; z++) array[x, y, z] = value;
    	}
    	public static void MemberSet<T>(this T[,,,] array, T value)
    	{
    		var X = array.GetLength(0); var Y = array.GetLength(1); var Z = array.GetLength(2); var W = array.GetLength(3);
    		for (var x = 0; x < X; x++) for (var y = 0; y < Y; y++) for (var z = 0; z < Z; z++) for (var w = 0; w < W; w++) array[x, y, z, w] = value;
    	}
    	public static string ToYesNo(this bool flag) { return flag ? "YES" : "NO"; }
    	public static int SetToMin(ref int min, int other) { return min = Math.Min(min, other); }
    	public static int SetToMax(ref int max, int other) { return max = Math.Max(max, other); }
    	public static long SetToMin(ref long min, long other) { return min = Math.Min(min, other); }
    	public static long SetToMax(ref long max, long other) { return max = Math.Max(max, other); }
    	public static Tuple<SortedDictionary<int, int>, SortedDictionary<int, int>> Compress(IEnumerable<int> coord, int width, int X)
    	{
    		var tmp = new SortedSet<int>();
    		foreach (var x in coord)
    		{
    			for (var w = -width; w <= width; w++)
    				if (x + w < 0 || x + w >= X) continue;
    				else if (tmp.Contains(x + w)) continue;
    				else tmp.Add(x + w);
    		}
    		var index = 0;
    		var inverse = new SortedDictionary<int, int>();
    		var dict = new SortedDictionary<int, int>();
    		foreach (var pair in tmp)
    		{
    			dict.Add(pair, index);
    			inverse.Add(index++, pair);
    		}
    		return new Tuple<SortedDictionary<int, int>, SortedDictionary<int, int>>(dict, inverse);
    	}
    	public static int MSB(uint n)
    	{
    		n |= (n >> 1);
    		n |= (n >> 2);
    		n |= (n >> 4);
    		n |= (n >> 8);
    		n |= (n >> 16);
    		return BitCount(n) - 1;
    	}
    	public static int BitCount(uint n)
    	{
    		n = (n & 0x55555555) + ((n >> 1) & 0x55555555);
    		n = (n & 0x33333333) + ((n >> 2) & 0x33333333);
    		n = (n & 0x0f0f0f0f) + ((n >> 4) & 0x0f0f0f0f);
    		n = (n & 0x00ff00ff) + ((n >> 8) & 0x00ff00ff);
    		return (int)((n & 0x0000ffff) + ((n >> 16) & 0x0000ffff));
    	}
    	public static int LSB(uint n)
    	{
    		n |= (n << 1);
    		n |= (n << 2);
    		n |= (n << 4);
    		n |= (n << 8);
    		n |= (n << 16);
    		return 32 - BitCount(n);
    	}
    	public static int MSB(ulong n)
    	{
    		n |= (n >> 1);
    		n |= (n >> 2);
    		n |= (n >> 4);
    		n |= (n >> 8);
    		n |= (n >> 16);
    		n |= (n >> 32);
    		return BitCount(n) - 1;
    	}
    	public static int BitCount(ulong n)
    	{
    		n = (n & 0x5555555555555555) + ((n >> 1) & 0x5555555555555555);
    		n = (n & 0x3333333333333333) + ((n >> 2) & 0x3333333333333333);
    		n = (n & 0x0f0f0f0f0f0f0f0f) + ((n >> 4) & 0x0f0f0f0f0f0f0f0f);
    		n = (n & 0x00ff00ff00ff00ff) + ((n >> 8) & 0x00ff00ff00ff00ff);
    		n = (n & 0x0000ffff0000ffff) + ((n >> 16) & 0x0000ffff0000ffff);
    		return (int)((n & 0x00000000ffffffff) + ((n >> 32) & 0x00000000ffffffff));
    	}
    	public static int LSB(ulong n)
    	{
    		n |= (n << 1);
    		n |= (n << 2);
    		n |= (n << 4);
    		n |= (n << 8);
    		n |= (n << 16);
    		n |= (n << 32);
    		return 64 - BitCount(n);
    	}
    	public static int Abs(this int n) { return Math.Abs(n); }
    	public static long Abs(this long n) { return Math.Abs(n); }
    	public static double Abs(this double n) { return Math.Abs(n); }
    	public static float Abs(this float n) { return Math.Abs(n); }
    	public static decimal Abs(this decimal n) { return Math.Abs(n); }
    	public static short Abs(this short n) { return Math.Abs(n); }
    	public static sbyte Abs(this sbyte n) { return Math.Abs(n); }
    	public static int Min(params int[] nums) { var min = int.MaxValue; foreach (var n in nums) min = Math.Min(min, n); return min; }
    	public static long Min(params long[] nums) { var min = long.MaxValue; foreach (var n in nums) min = Math.Min(min, n); return min; }
    	public static uint Min(params uint[] nums) { var min = uint.MaxValue; foreach (var n in nums) min = Math.Min(min, n); return min; }
    	public static ulong Min(params ulong[] nums) { var min = ulong.MaxValue; foreach (var n in nums) min = Math.Min(min, n); return min; }
    	public static double Min(params double[] nums) { var min = double.MaxValue; foreach (var n in nums) min = Math.Min(min, n); return min; }
    	public static decimal Min(params decimal[] nums) { var min = decimal.MaxValue; foreach (var n in nums) min = Math.Min(min, n); return min; }
    	public static int Max(params int[] nums) { var min = int.MinValue; foreach (var n in nums) min = Math.Max(min, n); return min; }
    	public static long Max(params long[] nums) { var min = long.MinValue; foreach (var n in nums) min = Math.Max(min, n); return min; }
    	public static uint Max(params uint[] nums) { var min = uint.MinValue; foreach (var n in nums) min = Math.Max(min, n); return min; }
    	public static ulong Max(params ulong[] nums) { var min = ulong.MinValue; foreach (var n in nums) min = Math.Max(min, n); return min; }
    	public static double Max(params double[] nums) { var min = double.MinValue; foreach (var n in nums) min = Math.Max(min, n); return min; }
    	public static decimal Max(params decimal[] nums) { var min = decimal.MinValue; foreach (var n in nums) min = Math.Max(min, n); return min; }
    }
    class RandomSFMT : Random
    {
    	int index, coin_bits, byte_pos, range, shift;
    	uint coin_save, byte_save, bse;
    	protected uint[] x = new uint[40];
    	static uint[] ParityData = { 0x00000001U, 0x00000000U, 0x00000000U, 0x20000000U };
    	public virtual void gen_rand_all()
    	{
    		int a = 0, b = 28, c = 32, d = 36; uint y; uint[] p = x;
    		do
    		{
    			y = p[a + 3] ^ (p[a + 3] << 24) ^ (p[a + 2] >> 8) ^ ((p[b + 3] >> 5) & 0xb5ffff7fU);
    			p[a + 3] = y ^ (p[c + 3] >> 8) ^ (p[d + 3] << 14);
    			y = p[a + 2] ^ (p[a + 2] << 24) ^ (p[a + 1] >> 8) ^ ((p[b + 2] >> 5) & 0xaff3ef3fU);
    			p[a + 2] = y ^ ((p[c + 2] >> 8) | (p[c + 3] << 24)) ^ (p[d + 2] << 14);
    			y = p[a + 1] ^ (p[a + 1] << 24) ^ (p[a] >> 8) ^ ((p[b + 1] >> 5) & 0x7fefcfffU);
    			p[a + 1] = y ^ ((p[c + 1] >> 8) | (p[c + 2] << 24)) ^ (p[d + 1] << 14);
    			y = p[a] ^ (p[a] << 24) ^ ((p[b] >> 5) & 0xf7fefffdU);
    			p[a] = y ^ ((p[c] >> 8) | (p[c + 1] << 24)) ^ (p[d] << 14);
    			c = d; d = a; a += 4; b += 4;
    			if (b == 40) b = 0;
    		} while (a != 40);
    	}
    	void period_certification()
    	{
    		uint work, inner = 0; int i, j;
    		index = 40; range = 0; coin_bits = 0; byte_pos = 0;
    		for (i = 0; i < 4; i++) inner ^= x[i] & ParityData[i];
    		for (i = 16; i > 0; i >>= 1) inner ^= inner >> i;
    		inner &= 1;
    		if (inner == 1) return;
    		for (i = 0; i < 4; i++) for (j = 0, work = 1; j < 32; j++, work <<= 1) if ((work & ParityData[i]) != 0) { x[i] ^= work; return; }
    	}
    	public void InitMt(uint s)
    	{
    		unchecked
    		{
    			x[0] = s;
    			for (uint p = 1; p < 40; p++) x[p] = s = 1812433253 * (s ^ (s >> 30)) + p;
    			period_certification();
    		}
    	}
    	public RandomSFMT(uint s) { InitMt(s); }
    	public void InitMtEx(uint[] init_key)
    	{
    		uint r, i, j, c, key_len = (uint)init_key.Length;
    		unchecked
    		{
    			for (i = 0; i < 40; i++) x[i] = 0x8b8b8b8b;
    			if (key_len + 1 > 40) c = key_len + 1; else c = 40;
    			r = x[0] ^ x[17] ^ x[39]; r = (r ^ (r >> 27)) * 1664525;
    			x[17] += r; r += key_len; x[22] += r; x[0] = r; c--;
    			for (i = 1, j = 0; j < c && j < key_len; j++)
    			{
    				r = x[i] ^ x[(i + 17) % 40] ^ x[(i + 39) % 40];
    				r = (r ^ (r >> 27)) * 1664525; x[(i + 17) % 40] += r;
    				r += init_key[j] + i; x[(i + 22) % 40] += r;
    				x[i] = r; i = (i + 1) % 40;
    			}
    			for (; j < c; j++)
    			{
    				r = x[i] ^ x[(i + 17) % 40] ^ x[(i + 39) % 40];
    				r = (r ^ (r >> 27)) * 1664525; x[(i + 17) % 40] += r; r += i;
    				x[(i + 22) % 40] += r; x[i] = r; i = (i + 1) % 40;
    			}
    			for (j = 0; j < 40; j++)
    			{
    				r = x[i] + x[(i + 17) % 40] + x[(i + 39) % 40];
    				r = (r ^ (r >> 27)) * 1566083941; x[(i + 17) % 40] ^= r;
    				r -= i; x[(i + 22) % 40] ^= r; x[i] = r; i = (i + 1) % 40;
    			}
    			period_certification();
    		}
    	}
    	public RandomSFMT(uint[] init_key) { InitMtEx(init_key); }
    	public RandomSFMT() : this((uint)(DateTime.Now.Ticks & 0xffffffff)) { }
    	public uint NextMt() { if (index == 40) { gen_rand_all(); index = 0; } return x[index++]; }
    	public int NextInt(int n) { return (int)(n * (1.0 / 4294967296.0) * NextMt()); }
    	public double NextUnif() { uint z = NextMt() >> 11, y = NextMt(); return (y * 2097152.0 + z) * (1.0 / 9007199254740992.0); }
    	public int NextBit() { if (--coin_bits == -1) { coin_bits = 31; return (int)(coin_save = NextMt()) & 1; } else return (int)(coin_save >>= 1) & 1; }
    	public int NextByte() { if (--byte_pos == -1) { byte_pos = 3; return (int)(byte_save = NextMt()) & 255; } else return (int)(byte_save >>= 8) & 255; }
    	public override int Next(int maxValue) { return Next(0, maxValue); }
    	protected override double Sample() { return NextUnif(); }
    	public override double NextDouble() { return NextUnif(); }
    	public override int Next() { return 1 + NextIntEx(int.MaxValue); }
    	public override void NextBytes(byte[] buffer) { for (var i = 0; i < buffer.Length; i++) buffer[i] = (byte)NextByte(); }
    	public override int Next(int min, int max) { return min + NextIntEx(max - min); }
    	public int NextIntEx(int range_)
    	{
    		uint y_, base_, remain_; int shift_;
    		if (range_ <= 0) return 0;
    		if (range_ != range)
    		{
    			bse = (uint)(range = range_);
    			for (shift = 0; bse <= (1UL << 30); shift++) bse <<= 1;
    		}
    		while (true)
    		{
    			y_ = NextMt() >> 1;
    			if (y_ < bse) return (int)(y_ >> shift);
    			base_ = bse; shift_ = shift; y_ -= base_;
    			remain_ = (1U << 31) - base_;
    			for (; remain_ >= (uint)range_; remain_ -= base_)
    			{
    				for (; base_ > remain_; base_ >>= 1) shift_--;
    				if (y_ < base_) return (int)(y_ >> shift_);
    				else y_ -= base_;
    			}
    		}
    	}
    }


Measured memory_bytes: 3640