Problem:
Score : 400 points

Problem Statement

You have N items and a bag of strength W.
The i-th item has a weight of w_i and a value of v_i.

You will select some of the items and put them in the bag.
Here, the total weight of the selected items needs to be at most W.

Your objective is to maximize the total value of the selected items.

Constraints

1 ≤ N ≤ 100

1 ≤ W ≤ 10^9

1 ≤ w_i ≤ 10^9

For each i = 2,3,...,N, w_1 ≤ w_i ≤ w_1 + 3.

1 ≤ v_i ≤ 10^7

W, each w_i and v_i are integers.

Input

Input is given from Standard Input in the following format:

N W
w_1 v_1
w_2 v_2
:
w_N v_N

Output

Print the maximum possible total value of the selected items.

Sample Input 1

4 6
2 1
3 4
4 10
3 4

Sample Output 1

11

The first and third items should be selected.

Sample Input 2

4 6
2 1
3 7
4 10
3 6

Sample Output 2

13

The second and fourth items should be selected.

Sample Input 3

4 10
1 100
1 100
1 100
1 100

Sample Output 3

400

You can take everything.

Sample Input 4

4 1
10 100
10 100
10 100
10 100

Sample Output 4

0

You can take nothing.

Solution in C# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
namespace Program {
    class MainClass {
        ////////////////////////////////////////////////////////////
        int N, W;
        int[] w, v;
        void Solve() {
            io.i(out N, out W);
            io.ini(out w, out v, N);
            N.REP(i => w[i] -= w[0]);//重さは4種類(0,1,2,3)
            //dp[i,j]i番目までの物で重さがj以下のときの価値の最大値
            long[,] dp = new long[N+1, 3*N+1];
            N.REP(i => dp.GetLength(1).REP(j => {
                if (j < w[i])
                    dp[i + 1, j] = dp[i, j];
                else
                    dp[i + 1, j] = Math.Max(dp[i, j], dp[i, j - w[i]] + v[i]);
            }));

            io.o(dp[N, W-w[0]]);

        }
        ////////////////////////////////////////////////////////////
        public static void Main() { new MainClass().Stream(); }
        IO io = new IO();
        void Stream() { Solve(); io.writeFlush(); }
        //void Stream() { Test(); io.writeFlush(); }
        void Test() { }
        #region MockMacro
        //cannot use break,continue,goto
        void FOR(int a, int b, Action<int> act) { for (int i = a; i < b; ++i) act(i); }
        void FORR(int a, int b, Action<int> act) { for (int i = a - 1; i >= b; --i) act(i); }
        #endregion
        ////////////////////////////////////////////////////////////
    }
    #region default
    class IO {
        TYPE tp;
        string[] nextBuffer; int BufferCnt; char[] cs = new char[] { ' ' };
        StreamWriter sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        public IO() { nextBuffer = new string[0]; BufferCnt = 0; Console.SetOut(sw); tp = new TYPE(); }
        public string Next() {
            if (BufferCnt < nextBuffer.Length) return nextBuffer[BufferCnt++];
            string st = Console.ReadLine();
            while (st == "") st = Console.ReadLine();
            nextBuffer = st.Split(cs, StringSplitOptions.RemoveEmptyEntries);
            BufferCnt = 0;
            return nextBuffer[BufferCnt++];
        }
        public string String => Next();
        public char Char => char.Parse(String);
        public int Int => int.Parse(String);
        public long Long => long.Parse(String);
        public double Double => double.Parse(String);
        public string[] arr => Console.ReadLine().Split(' ');
        public char[] arrChar => Array.ConvertAll(arr, char.Parse);
        public int[] arrInt => Array.ConvertAll(arr, int.Parse);
        public long[] arrLong => Array.ConvertAll(arr, long.Parse);
        public double[] arrDouble => Array.ConvertAll(arr, double.Parse);
        public T i<T>() { return tp.suitType<T>(String); }
        public void i<T>(out T v) { v = tp.suitType<T>(String); }
        public void i<T, U>(out T v1, out U v2) { i(out v1); i(out v2); }
        public void i<T, U, V>(out T v1, out U v2, out V v3) { i(out v1); i(out v2); i(out v3); }
        public void i<T, U, V, W>(out T v1, out U v2, out V v3, out W v4) {
            i(out v1); i(out v2); i(out v3); i(out v4);
        }
        public void i<T, U, V, W, X>(out T v1, out U v2, out V v3, out W v4, out X v5) {
            i(out v1); i(out v2); i(out v3); i(out v4); i(out v5);
        }
        public void ini<T>(out T[] a, int n) { a = new T[n]; for (int i = 0; i < n; i++) a[i] = tp.suitType<T>(String); }
        public void ini<T, U>(out T[] a, out U[] b, int n) {
            a = new T[n]; b = new U[n]; for (int i = 0; i < n; i++) { a[i] = i<T>(); b[i] = i<U>(); }
        }
        public void ini<T, U, V>(out T[] a, out U[] b, out V[] c, int n) {
            a = new T[n]; b = new U[n]; c = new V[n];
            for (int i = 0; i < n; i++) { a[i] = i<T>(); b[i] = i<U>(); c[i] = i<V>(); }
        }
        public void ini<T>(out T[,] a, int h, int w) {
            a = new T[h, w]; for (int i = 0; i < h; i++) for (int j = 0; j < w; j++) a[i, j] = i<T>();
        }
        public void o<T>(T v) { Console.WriteLine(v); }
        public void o<T>(params T[] a) { Array.ForEach(a, n => o(n)); }
        public void o<T>(T[,] a) { a.GetLength(0).REP(i => { a.GetLength(1).REP(j => or(a[i, j] + " ")); br(); }); }
        public void ol<T>(T v) { Console.Write(v + " "); }
        public void ol<T>(params T[] a) { o(connect<T>(a)); }
        public void or<T>(T a) { Console.Write(a); }
        public void br() { o(""); }
        public void writeFlush() { Console.Out.Flush(); }
        private string connect<T>(params T[] s) { return string.Join(" ", s); }
    }
    class TYPE {
        public bool typeEQ<T, U>() { return typeof(T).Equals(typeof(U)); }
        public T convertType<T, U>(U v) { return (T)Convert.ChangeType(v, typeof(T)); }
        public T suitType<T>(string s) {
            if (typeEQ<T, int>()) return convertType<T, int>(int.Parse(s));
            if (typeEQ<T, long>()) return convertType<T, long>(long.Parse(s));
            if (typeEQ<T, double>()) return convertType<T, double>(double.Parse(s));
            if (typeEQ<T, char>()) return convertType<T, char>(char.Parse(s));
            return convertType<T, string>(s);
        }
    }
    class PQueue<T> where T : IComparable {
        public List<T> heap;private Comparison<T> comp;private IComparer<T> comparer;
        private int size;private int type;//type=0->min
        public PQueue(int type = 0) : this(Comparer<T>.Default) { this.type = type; }
        public PQueue(IComparer<T> comparer) : this(16, comparer.Compare) { this.comparer = comparer; }
        public PQueue(Comparison<T> comparison) : this(16, comparison) { }
        public PQueue(int capacity, Comparison<T> comparison) { this.heap = new List<T>(capacity); this.comp = comparison; }
        public void Enqueue(T item) {
            this.heap.Add(item); var i = size++;
            while (i > 0) { var p = (i - 1) >> 1; if (Compare(this.heap[p], item) <= 0) break; this.heap[i] = heap[p]; i = p; }
            this.heap[i] = item;
        }
        public T Dequeue() {
            var ret = this.heap[0]; var x = this.heap[--size]; var i = 0;
            while ((i << 1) + 1 < size) {
                var a = (i << 1) + 1; var b = (i << 1) + 2; if (b < size && Compare(heap[b], heap[a]) < 0) a = b;
                if (Compare(heap[a], x) >= 0) break; heap[i] = heap[a]; i = a;
            }
            heap[i] = x; heap.RemoveAt(size);
            return ret;
        }
        public T Peek() { return heap[0]; }
        public int Count { get { return size; } }
        public bool Any() { return size > 0; }
        public bool Empty() { return !Any(); }
        public bool Contains(T v) { return heap.Contains(v); }
        private int Compare(T x, T y) { return type == 0 ? x.CompareTo(y) : y.CompareTo(x); }
    }
    #endregion
    #region other
    class Mat {
        public int mod = 1000000007;//10^9+7
        public long Pow(long a, long b) {
            if (b == 0) return 1;
            if (b % 2 == 1) return (a % mod * Pow(a % mod, b - 1) % mod) % mod;
            else return Pow(a * a % mod, b / 2) % mod;
        }
        public long Fact(long n) {
            long ret = 1;
            for (long i = 1; i <= n; i++)
                ret = (ret * i) % mod;
            return ret;
        }
        public long C(long n, long r) {
            if (r == 0 || n == r) return 1;
            if (n == 0) return 0;
            if (n < 0 || n < r) throw new ArgumentException("n,r invalid");
            else return (Fact(n) % mod * Pow((Fact(n - r) % mod * Fact(r) % mod) % mod, mod - 2) % mod) % mod;
        }
        public long DupC(long n, long r) { return C(n + r - 1, r); }
        public long P(long n, long r) { return Fact(n) / (Fact(n - r)); }//test
        public bool isPrime(long n) {
            if (n == 2) return true; if (n < 2 || n % 2 == 0) return false;
            for (long v = 3; v <= (long)Math.Sqrt(n); v += 2) if (n % v == 0) return false;
            return true;
        }
        public long LCM(long a, long b) { return a * (b / GCD(a, b)); }
        public long LCM(params long[] a) { return a.Aggregate((v, n) => LCM(v, n)); }
        public long GCD(long a, long b) { if (a < b) Swap(ref a, ref b); return b == 0 ? a : GCD(b, a % b); }
        public long GCD(params long[] array) { return array.Aggregate((v, n) => GCD(v, n)); }
        public T Max<T>(params T[] a) { return a.Max(); }
        public T Min<T>(params T[] a) { return a.Min(); }
        public void Swap<T>(ref T a, ref T b) { T tmp = a; a = b; b = tmp; }
        public double Dis(int x1, int y1, int x2, int y2) { return Math.Sqrt(Math.Pow((x2 - x1), 2) + Math.Pow((y2 - y1), 2)); }
        public int mDis(int x1, int y1, int x2, int y2) { return Math.Abs(x1 - x2) + Math.Abs(y1 - y2); }
        public int Dig2Num(IEnumerable<int> enu) {//test
            int ret = 0;
            foreach (var v in enu) {
                ret *= 10;
                ret += v;
            }
            return ret;
        }
        public int Digit(long n) { return (n == 0) ? 1 : (int)Math.Log10(n) + 1; }
        public int DigVal(int n, int dig) { return (n % (int)Pow(10, dig)) / (int)Pow(10, dig - 1); }
        public int[] DigValArr(int n) { int[] ret = new int[Digit(n)]; ret.Length.REP(i => ret[i] = DigVal(n, i + 1)); return ret; }
        public long Tousa(long a, long d, long n) { return a + (n - 1) * d; }
        public long TousaSum(long a, long d, long n) { return n * (2 * a + (n - 1) * d) / 2; }
        public IEnumerable<int[]> eunP(int[] Arr, int Use = -1) {//列挙順列
            Use = (Use != -1) ? Use : Arr.Length; if (Use == 0 || Arr.Length < Use) yield break;
            var s = new Stack<List<int>>();
            Arr.Length.REPR(i => s.Push(new List<int>() { i }));
            while (s.Count > 0) {
                var cur = s.Pop();
                if (cur.Count == Use) {
                    var ret = new List<int>(); cur.ForEach(X => ret.Add(Arr[X]));
                    yield return ret.ToArray();
                } else
                    Arr.Length.REPR(i => { if (!cur.Contains(i)) s.Push(new List<int>(cur) { i }); });
            }
        }
        public IEnumerable<int[]> enuC(int[] Arr, int Use = -1) {//列挙組み合わせ
            Use = (Use != -1) ? Use : Arr.Length; if (Use == 0 || Arr.Length < Use) yield break;
            var s = new Stack<Tuple<int, List<int>>>();
            Arr.Length.REPR(i => s.Push(Tuple.Create(i, new List<int>() { Arr[i] })));
            while (s.Count > 0) {
                var cur = s.Pop();
                if (cur.Item2.Count == Use)
                    yield return cur.Item2.ToArray();
                else
                    for (int i = Arr.GetUpperBound(0); i > cur.Item1; i--)
                        s.Push(Tuple.Create(i, new List<int>(cur.Item2) { Arr[i] }));
            }
        }
        public IEnumerable<int[]> eunDupP(int[] Arr, int Use = -1) {//列挙重複順列
            Use = (Use != -1) ? Use : Arr.Length; if (Use == 0) yield break; var s = new Stack<List<int>>();
            Arr.Length.REPR(i => s.Push(new List<int>() { Arr[i] }));
            while (s.Count > 0) {
                var cur = s.Pop();
                if (cur.Count == Use)
                    yield return cur.ToArray();
                else
                    Arr.Length.REPR(i => s.Push(new List<int>(cur) { Arr[i] }));
            }
        }
        public IEnumerable<int[]> enuDupC(int[] Arr, int Use = -1) {//列挙組み合わせ
            Use = (Use != -1) ? Use : Arr.Length; if (Use == 0) yield break;
            var s = new Stack<Tuple<int, List<int>>>();
            Arr.Length.REPR(i => s.Push(Tuple.Create(i, new List<int>() { Arr[i] })));
            while (s.Count > 0) {
                var cur = s.Pop();
                if (cur.Item2.Count == Use)
                    yield return cur.Item2.ToArray();
                else
                    for (int i = Arr.GetUpperBound(0); i >= cur.Item1; i--)
                        s.Push(Tuple.Create(i, new List<int>(cur.Item2) { Arr[i] }));
            }
        }
        public IEnumerable<long[]> enuPart(string str) {
            var s = new Stack<Tuple<string, List<long>, int>>();
            s.Push(Tuple.Create(str[0].ToString(), new List<long>(), 1));
            while (s.Count > 0) {
                var cur = s.Pop();
                if (cur.Item3 >= str.Length) {
                    yield return (new List<long>(cur.Item2) { cur.Item1.toLong() }).ToArray();
                } else {
                    //繋げる
                    s.Push(Tuple.Create(cur.Item1 + str[cur.Item3], new List<long>(cur.Item2), cur.Item3 + 1));
                    //繋がない
                    s.Push(Tuple.Create(str[cur.Item3].ToString(), new List<long>(cur.Item2) { cur.Item1.toLong() }, cur.Item3 + 1));
                }
            }
        }
    }
    class Time {
        public int[] M = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
        public int[] D = { 31, -1, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
        public Time() { D[1] = 28; }
        public Time(int y) { D[1] = isLeapYear(y) ? 29 : 28; }
        public bool isLeapYear(int y) { return (y % 400 == 0 || (y % 4 == 0 && y % 100 != 0)); }
    }
    #endregion
    #region Data
    class AssociativeArray<T> : IEnumerable {//hack:KeyValuePairの利用に制限がかかる
        public Dictionary<T, int> dic;
        public AssociativeArray() { dic = new Dictionary<T, int>(); }
        public AssociativeArray(params T[] a) { dic = new Dictionary<T, int>(); Add(a); }
        public void Add(params T[] a) { a.Length.REP(i => { if (!conK(a[i])) dic[a[i]] = 0; dic[a[i]]++; }); }
        public void Set(T k, int v) { if (!dic.ContainsKey(k)) dic[k] = 0; dic[k] = v; }
        public void Remove(params T[] a) { a.Length.REP(i => { if (conK(a[i])) dic.Remove(a[i]); }); }
        public T[] Keys() { return dic.Keys.ToArray<T>(); }
        public int Val(T k) { return (dic.ContainsKey(k)) ? dic[k] : 0; }
        public int ValSum => dic.Values.Sum();
        public int KeyNum => dic.Keys.Count;
        public int MaxVal => dic.Values.Max();
        public int MinVal => dic.Values.Min();
        public T MaxKey => dic.First(d => d.Value == MaxVal).Key;
        public T MinKey => dic.First(d => d.Value == MinVal).Key;
        public bool conK(T k) { return dic.ContainsKey(k); }
        public bool anyK(params T[] k) { return k.Any(key => conK(key)); }
        public bool allK(params T[] k) { return k.All(key => conK(key)); }
        public void Show() { foreach (var v in dic) { Console.WriteLine(v.Key + " : " + v.Value); } }
        public IEnumerator GetEnumerator() { foreach (var kp in dic) yield return kp; }
        //:sort->array
    }
    class Index {
        public int[] Comp(int[] bef) {
            int[] aft = new int[bef.Length];
            var tmp = bef.Distinct().OrderBy(v => v).Select((v, i) => new { v, i }).ToDictionary(p => p.v, p => p.i);
            aft = bef.Select(v => tmp[v]).ToArray();
            return aft;
        }
    }
    class BasicGraph {//けす
        public List<Tuple<int, long>>[] G;
        public void Init(int n) { G = new List<Tuple<int, long>>[n + 1]; G.Length.REP(i => G[i] = new List<Tuple<int, long>>()); }
        public void Dir(int[] f, int[] t) { f.Length.REP(i => G[f[i]].Add(Tuple.Create(t[i], 1L))); }
        public void Dir(int[] f, int[] t, long[] c) { f.Length.REP(i => G[f[i]].Add(Tuple.Create(t[i], c[i]))); }
        public void NonDir(int[] f, int[] t) { f.Length.REP(i => { G[f[i]].Add(Tuple.Create(t[i], 1L)); G[t[i]].Add(Tuple.Create(f[i], 1L)); }); }
        public void NonDir(int[] f, int[] t, long[] c) { f.Length.REP(i => { G[f[i]].Add(Tuple.Create(t[i], c[i])); G[t[i]].Add(Tuple.Create(f[i], c[i])); }); }
    }
    class TreeDis {//TODO:shortestPath
        public List<Tuple<long, long>>[] g; public long[] a2other; private int type;
        public TreeDis(int type = 0) { this.type = type; }//0->bfs,other->dfs
        public void Init(long n) { g = new List<Tuple<long, long>>[n + 1]; g.Length.REP(i => g[i] = new List<Tuple<long, long>>()); }
        public void Run(long[] a, long[] b) { a.Length.REP(i => { g[a[i]].Add(Tuple.Create(b[i], 1L)); g[b[i]].Add(Tuple.Create(a[i], 1L)); }); }
        public void Run(long[] a, long[] b, long[] w) { a.Length.REP(i => { g[a[i]].Add(Tuple.Create(b[i], w[i])); g[b[i]].Add(Tuple.Create(a[i], w[i])); }); }
        public long[] a2iArr(long a) { a2other = new long[g.Count()]; if (type == 0) BFS(a); else DFS(a); return a2other; }
        private void BFS(long a) {
            var q = new Queue<Tuple<long, long>>(); q.Enqueue(Tuple.Create(a, -1L));
            while (q.Count > 0) {
                var c = q.Dequeue();
                foreach (var v in g[c.Item1]) {
                    if (v.Item1 == c.Item2) continue;
                    a2other[v.Item1] = a2other[c.Item1] + v.Item2; q.Enqueue(Tuple.Create(v.Item1, c.Item1));
                }
            }
        }
        private void DFS(long a) {
            var s = new Stack<Tuple<long, long>>(); s.Push(Tuple.Create(a, -1L));
            while (s.Count > 0) {
                var c = s.Pop();
                foreach (var v in g[c.Item1]) {
                    if (v.Item1 == c.Item2) continue;
                    a2other[v.Item1] = a2other[c.Item1] + v.Item2; s.Push(Tuple.Create(v.Item1, c.Item1));
                }
            }
        }
    }
    class ShortestPath {
        public long INF = (long)1e15; protected int I = -1; protected int V; protected int E; public long[] cost;
        public List<Tuple<int, long>>[] Adj; protected bool isNonDir = true;
        public void Init(int n) { I = n + 1; V = n; Adj = new List<Tuple<int, long>>[I]; I.REP(i => Adj[i] = new List<Tuple<int, long>>()); }
        public void AddPath(int f, int t, long c) {
            E++;
            if (isNonDir) {
                Adj[f].Add(Tuple.Create(t, c)); Adj[t].Add(Tuple.Create(f, c));
            } else {
                Adj[f].Add(Tuple.Create(t, c));
            }
        }
        public void AddPath(int[] f, int[] t, long[] c) { f.Length.REP(i => AddPath(f[i], t[i], c[i])); }
    }
    class Dijkstra : ShortestPath {//隣接対応後検証不足,有向
        public long MinCost(int f, int t) {
            cost = new long[I]; cost.Set(INF); cost[f] = 0;
            var pq = new PQueue<Tuple<int, long>>(); pq.Enqueue(Tuple.Create(f, 0L));//(from,cost)
            while (pq.Count > 0) {
                var cur = pq.Dequeue();
                if (cost[cur.Item1] < cur.Item2) continue; Adj[cur.Item1].Count.REP(i => {
                    var tmp = Adj[cur.Item1][i];
                    if (cost[tmp.Item1] > cost[cur.Item1] + tmp.Item2) {
                        cost[tmp.Item1] = cost[cur.Item1] + tmp.Item2; pq.Enqueue(Tuple.Create(tmp.Item1, cost[tmp.Item1]));
                    }
                });
            }
            return cost[t];
        }
    }
    class BellmanFord : ShortestPath {
        private bool[] neg;
        public BellmanFord() { }
        public BellmanFord(bool isNonDir) { this.isNonDir = isNonDir; }
        public long MinCost(int f, int t) {
            cost = new long[I]; cost.Set(INF); cost[f] = 0; neg = new bool[I];
            for (int i = 0; i < I - 1; i++) {
                I.REP(j => Adj[j].Count.REP(k => {
                    var cur = Adj[j][k];
                    if (cost[cur.Item1] > cost[j] + cur.Item2)
                        cost[cur.Item1] = cost[j] + cur.Item2;
                }));
            }
            for (int i = 0; i < I; i++) {
                I.REP(j => Adj[j].Count.REP(k => {
                    var cur = Adj[j][k];
                    if (cost[cur.Item1] > cost[j] + cur.Item2) {
                        cost[cur.Item1] = cost[j] + cur.Item2;
                        neg[cur.Item1] = true;
                    }
                    if (neg[j]) neg[cur.Item1] = true;
                }));
            }
            return cost[t];
        }
        public bool loopExist() { return neg[I - 1]; }
    }
    class WarshallFloyd {//そのうちAdjとどっちがいいか...TODO:ジェネリック
        private int E; private int INF = (int)1e9; public long[,] G;
        public void Init(int n) { E = n + 1; G = new long[E, E]; G.Set(INF); E.REP(i => G[i, i] = 0); }
        public void AddPath(int f, int t, long c) { G[f, t] = c; G[t, f] = c; }
        public void AddPath(int[] f, int[] t) { f.Length.REP(i => AddPath(f[i], t[i], 1)); }
        public void AddPath(int[] f, int[] t, long[] c) { f.Length.REP(i => AddPath(f[i], t[i], c[i])); }
        public void Run() { G = MinCostArr(); }
        public long[,] MinCostArr() { E.REP(i => E.REP(j => E.REP(k => G[j, k] = Math.Min(G[j, k], G[j, i] + G[i, k])))); return G; }
    }
    class UnionFind {
        public long[] parent; public long[] depth; private int I;
        public void Init(int n) { I = n + 1; parent = new long[I]; depth = new long[I]; I.REP(i => parent[i] = i); }
        public long Find(long x) { return (parent[x] == x) ? x : parent[x] = Find(parent[x]); }
        public void Unite(long x, long y) {
            x = Find(x); y = Find(y); if (x == y) return;
            if (depth[x] < depth[y]) parent[x] = y; else { parent[y] = x; if (depth[x] == depth[y]) depth[x]++; }
        }
        public bool Same(int a, int b) { return Find(a) == Find(b); }
        public long Size(int x) { return depth[Find(x)]; }
    }
    class Kruskal : ShortestPath {//TODO:test
        public long Run() {
            var li = new List<Tuple<int, int, long>>();
            I.REP(i => { foreach (var t in Adj[i]) { li.Add(Tuple.Create(i, t.Item1, t.Item2)); } });
            li = li.OrderBy(t => t.Item3).ToList();
            var uf = new UnionFind(); uf.Init(V); long ret = 0;
            foreach (var t in li) { if (!uf.Same(t.Item1, t.Item2)) { ret += t.Item3; uf.Unite(t.Item1, t.Item2); } }
            return ret;
        }
    }
    #endregion
    #region Ex
    static class StringEX {
        public static string Reversed(this string s) { return string.Join("", s.Reverse()); }
        public static string Repeat(this string s, int n) { return string.Concat(Enumerable.Repeat(s, n).ToArray()); }
        public static int toInt(this string s) { int n; return (int.TryParse(s.TrimStart('0'), out n)) ? n : 0; }
        public static int toInt(this char c) { return toInt(c.ToString()); }
        public static int toInt(this char[] c) { return toInt(new string(c)); }
        public static long toLong(this string s) { long n; return (long.TryParse(s.TrimStart('0'), out n)) ? n : (long)0; }
        public static long toLong(this char c) { return toLong(c.ToString()); }
        public static long toLong(this char[] c) { return toLong(new string(c)); }
        public static string toString(this char[] c) { return new string(c); }
    }
    static class NumericEx {
        public static string pad0<T>(this T v, int n) { return v.ToString().PadLeft(n, '0'); }
        public static double RoundOff(this double v, int n) { return Math.Round(v, n - 1, MidpointRounding.AwayFromZero); }
        public static bool Odd(this int v) { return v % 2 != 0; }
        public static bool Odd(this long v) { return v % 2 != 0; }
        public static void REP(this int v, Action<int> act) { for (int i = 0; i < v; ++i) act(i); }
        public static void REPR(this int v, Action<int> act) { for (int i = v - 1; i >= 0; --i) act(i); }
    }
    static class ArrayEX {
        public static T[] Sort<T>(this T[] a) { Array.Sort(a); return a; }
        public static T[] SortR<T>(this T[] a) { Array.Sort(a); Array.Reverse(a); return a; }
        public static void Set<T>(this T[] a, T v) { a.Length.REP(i => a[i] = v); }
        public static void Set<T>(this T[,] a, T v) { a.GetLength(0).REP(i => a.GetLength(1).REP(j => a[i, j] = v)); }
    }
    static class BitEx {
        public static bool Any(this BitArray b) { foreach (bool f in b) if (f) return true; return false; }
        public static bool All(this BitArray b) { foreach (bool f in b) if (!f) return false; return true; }
        public static bool None(this BitArray b) { return !Any(b); }
        public static void Flip(this BitArray b, int index) { b.Set(index, !b.Get(index)); }
    }
    static class IEnumerableEx {
        public static void ForEach<T>(this IEnumerable<T> s, Action<T> act) { foreach (var v in s) act(v); }
        public static void ForEach<T>(this IEnumerable<T> s, Action<T, int> act) {
            foreach (var v in s.Select((x, i) => new { V = x, I = i })) act(v.V, v.I);
        }
    }
    #endregion
}