Problem:
Score : 400 points

Problem Statement

Consider a grid with H rows and W columns of squares. Let (r, c) denote the square at the r-th row from the top and the c-th column from the left.
Each square is painted black or white.

The grid is said to be good if and only if the following condition is satisfied:

From (1, 1), we can reach (H, W) by moving one square right or down repeatedly, while always being on a white square.

Note that (1, 1) and (H, W) must be white if the grid is good.

Your task is to make the grid good by repeating the operation below. Find the minimum number of operations needed to complete the task. It can be proved that you can always complete the task in a finite number of operations.

Choose four integers r_0, c_0, r_1, c_1(1 \leq r_0 \leq r_1 \leq H, 1 \leq c_0 \leq c_1 \leq W). For each pair r, c (r_0 \leq r \leq r_1, c_0 \leq c \leq c_1), invert the color of (r, c) - that is, from white to black and vice versa.

Constraints

2 \leq H, W \leq 100

Input

Input is given from Standard Input in the following format:

H W
s_{11} s_{12} \cdots s_{1W}
s_{21} s_{22} \cdots s_{2W}
\vdots
s_{H1} s_{H2} \cdots s_{HW}

Here s_{rc} represents the color of (r, c) - # stands for black, and . stands for white.

Output

Print the minimum number of operations needed.

Sample Input 1

3 3
.##
.#.
##.

Sample Output 1

1

Do the operation with (r_0, c_0, r_1, c_1) = (2, 2, 2, 2) to change just the color of (2, 2), and we are done.

Sample Input 2

2 2
#.
.#

Sample Output 2

2

Sample Input 3

4 4
..##
#...
###.
###.

Sample Output 3

0

No operation may be needed.

Sample Input 4

5 5
.#.#.
#.#.#
.#.#.
#.#.#
.#.#.

Sample Output 4

4

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Text;
using static System.Math;
using static Solve.Methods;
using static Solve.Input;
using static Solve.Output;
using pii = Solve.Pair<int, int>;
using pll = Solve.Pair<long, long>;
using pli = Solve.Pair<long, int>;
using pil = Solve.Pair<int, long>;
using pss = Solve.Pair<string, string>;
using psi = Solve.Pair<string, int>;
using lint = System.Collections.Generic.List<int>;
using llong = System.Collections.Generic.List<long>;
using lstr = System.Collections.Generic.List<string>;
using llint = System.Collections.Generic.List<System.Collections.Generic.List<int>>;
using llstr = System.Collections.Generic.List<System.Collections.Generic.List<long>>;
using lllong = System.Collections.Generic.List<System.Collections.Generic.List<string>>;
using lii = System.Collections.Generic.List<Solve.Pair<int, int>>;
using lll = System.Collections.Generic.List<Solve.Pair<long, long>>;
using lli = System.Collections.Generic.List<Solve.Pair<long, int>>;
using lil = System.Collections.Generic.List<Solve.Pair<int, long>>;
using ll = System.Int64;

namespace Solve
{
    public class Solver
    {
        public void Main()
        {
            int H, W;
            In(out H, out W);
            var grid = new bool[H, W];
            // # 黒
            for (int i = 0; i < H; i++)
            {
                var s = Read;
                for (int j = 0; j < W; j++) grid[i, j] = s[j] == '#';
            }

            var dp = new int[H, W];
            if (grid[0, 0]) dp[0, 0] = 1;
            for (int i = 0; i < H; i++)
            {
                for (int j = 0; j < W; j++)
                {
                    if (j == 0)
                    {
                        if (i == 0) continue;
                        if (grid[i, j]) dp[i, j] = dp[i - 1, 0] + 1;
                        else dp[i, j] = dp[i - 1, 0];
                        continue;
                    }

                    if (i == 0)
                    {
                        if (grid[i, j]) dp[i, j] = dp[i, j - 1] + 1;
                        else dp[i, j] = dp[i, j - 1];
                        continue;
                    }

                    dp[i, j] = Min(dp[i - 1, j], dp[i, j - 1]);
                    if (grid[i, j]) dp[i, j]++;
                }
            }

            cout = dp[H - 1, W - 1];



        }


        // ReSharper disable UnusedMember.Local
        private const int MOD = (int) 1e9 + 7,
            INF = 1000000010;

        private const long LINF = 1000000000000000100;
    }

    // ライブラリ置き場ここから
    
    
    
    // ライブラリ置き場ここまで

    #region Templete

#if !LOCAL
namespace Library { }
#endif
    public static class Methods
    {
        public static readonly int[] dx = {-1, 0, 0, 1};
        public static readonly int[] dy = {0, 1, -1, 0};


        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static void Assert(bool b, string message = null)
        {
            if (!b) throw new Exception(message ?? "Assert failed.");
        }

        /*
        public static Comparison<T> greater<T>() 
            where T : IComparable<T> 
            => (a, b) => b.CompareTo(a);
        */

        public static string JoinSpace<T>(this IEnumerable<T> source) => source.Join(" ");
        public static string JoinEndline<T>(this IEnumerable<T> source) => source.Join("\n");
        public static string Join<T>(this IEnumerable<T> source, string s) => string.Join(s, source);
        public static string Join<T>(this IEnumerable<T> source, char c) => string.Join(c.ToString(), source);

        /// <summary>
        /// <see cref="Pair{T1, T2}"/> クラスのインスタンスを作成します。
        /// </summary>
        /// <typeparam name="T1">firstの型</typeparam>
        /// <typeparam name="T2">secondの型</typeparam>
        /// <param name="first">firstの値</param>
        /// <param name="second">secondの値</param>
        /// <returns>作成した<see cref="Pair{T1, T2}"/> クラスのインスタンス</returns>
        public static Pair<T1, T2> make_pair<T1, T2>(T1 first, T2 second)
            where T1 : IComparable<T1>
            where T2 : IComparable<T2>
            => new Pair<T1, T2>(first, second);

        /// <summary>aとbをスワップします。</summary>
        public static void Swap<T>(ref T a, ref T b) where T : struct
        {
            var tmp = b;
            b = a;
            a = tmp;
        }

        /// <summary>aとbの最大公約数を求めます。</summary>
        /// <returns>aとbの最大公約数</returns>
        public static long Gcd(long a, long b)
        {
            while (true)
            {
                if (a < b) Swap(ref a, ref b);
                if (a % b == 0) return b;
                var x = a;
                a = b;
                b = x % b;
            }
        }

        /// <summary>aとbの最小公倍数を求めます。</summary>
        /// <returns>aとbの最小公倍数</returns>
        public static long Lcm(long a, long b) => a / Gcd(a, b) * b;

        /// <summary>
        /// 指定した数値が素数であるかを判定します。
        /// </summary>
        /// <remarks>計算量 (sqrt(value)) </remarks>
        /// <param name="value">判定する数値</param>
        /// <returns>value が素数であるか</returns>
        public static bool IsPrime(long value)
        {
            if (value <= 1) return false;
            for (long i = 2; i * i <= value; i++)
                if (value % i == 0)
                    return false;
            return true;
        }

        /// <summary>
        /// <see cref="a"/> ^ <see cref="b"/> (mod <see cref="p"/>) を求める
        /// </summary>
        /// <returns><see cref="a"/> ^ <see cref="b"/> (mod <see cref="p"/>) の値</returns>
        public static long PowMod(long a, long b, long p)
        {
            long res = 1;
            while (b > 0)
            {
                if (b % 2 != 0) res = res * a % p;
                a = a * a % p;
                b >>= 1;
            }

            return res;
        }

        /// <summary>
        /// mod pにおけるaの逆元を求めます。
        /// </summary>
        /// <param name="a"></param>
        /// <param name="p">法</param>
        /// <returns></returns>
        public static long ModInv(long a, long p)
            => PowMod(a, p - 2, p);

        public static int DivCeil(int left, int right)
            => left / right + (left % right == 0 ? 0 : 1);

        public static long DivCeil(long left, long right)
            => left / right + (left % right == 0L ? 0L : 1L);

        /// <summary>
        /// src の順列を求めます。
        /// </summary>
        /// <typeparam name="T">型</typeparam>
        /// <param name="src">順列を求める配列</param>
        /// <returns>src の順列</returns>
        public static IEnumerable<T[]> Permutations<T>(IEnumerable<T> src)
        {
            var ret = new List<T[]>();
            Search(ret, new Stack<T>(), src.ToArray());
            return ret;
        }

        private static void Search<T>(ICollection<T[]> perms, Stack<T> stack, T[] a)
        {
            int N = a.Length;
            if (N == 0) perms.Add(stack.Reverse().ToArray());
            else
            {
                var b = new T[N - 1];
                Array.Copy(a, 1, b, 0, N - 1);
                for (int i = 0; i < a.Length; ++i)
                {
                    stack.Push(a[i]);
                    Search(perms, stack, b);
                    if (i < b.Length) b[i] = a[i];
                    stack.Pop();
                }
            }
        }

        /// <summary>
        /// 指定した条件を満たす最小の数値を返します。
        /// </summary>
        /// <param name="low">検索する数値の最小値</param>
        /// <param name="high">検索する数値の最大値</param>
        /// <param name="expression">条件</param>
        /// <returns>条件を満たす最小の数値</returns>
        public static long BinarySearch(long low, long high, Func<long, bool> expression)
        {
            while (low < high)
            {
                long middle = (high - low) / 2 + low;
                if (!expression(middle))
                    high = middle;
                else
                    low = middle + 1;
            }

            return high;
        }

        /// <summary>
        /// 指定した値以上の先頭のインデクスを返します。
        /// </summary>
        /// <typeparam name="T">比較する値の型</typeparam>
        /// <param name="arr">対象の配列（※ソート済みであること）</param>
        /// <param name="start">開始インデクス [inclusive]</param>
        /// <param name="end">終了インデクス [exclusive]</param>
        /// <param name="value">検索する値</param>
        /// <param name="comparer">比較関数(インターフェイス)</param>
        /// <returns>指定した値以上の先頭のインデクス</returns>
        public static int LowerBound<T>(T[] arr, int start, int end, T value, IComparer<T> comparer)
        {
            int low = start;
            int high = end;
            while (low < high)
            {
                var mid = ((high - low) >> 1) + low;
                if (comparer.Compare(arr[mid], value) < 0)
                    low = mid + 1;
                else
                    high = mid;
            }

            return low;
        }

        /// <summary>
        /// 指定した値以上の先頭のインデクスを返します。
        /// </summary>
        /// <typeparam name="T">比較する値の型</typeparam>
        /// <param name="arr">対象の配列（※ソート済みであること）</param>
        /// <param name="value">検索する値</param>
        /// <returns>指定した値以上の先頭のインデクス</returns>
        public static int LowerBound<T>(T[] arr, T value) where T : IComparable
        {
            return LowerBound(arr, 0, arr.Length, value, Comparer<T>.Default);
        }

        /// <summary>
        /// 指定した値より大きい先頭のインデクスを返します。
        /// </summary>
        /// <typeparam name="T">比較する値の型</typeparam>
        /// <param name="arr">対象の配列（※ソート済みであること）</param>
        /// <param name="start">開始インデクス [inclusive]</param>
        /// <param name="end">終了インデクス [exclusive]</param>
        /// <param name="value">検索する値</param>
        /// <param name="comparer">比較関数(インターフェイス)</param>
        /// <returns>指定した値より大きい先頭のインデクス</returns>
        public static int UpperBound<T>(T[] arr, int start, int end, T value, IComparer<T> comparer)
        {
            int low = start;
            int high = end;
            while (low < high)
            {
                var mid = ((high - low) >> 1) + low;
                if (comparer.Compare(arr[mid], value) <= 0)
                    low = mid + 1;
                else
                    high = mid;
            }

            return low;
        }

        /// <summary>
        /// 指定した値より大きい先頭のインデクスを返します。
        /// </summary>Z
        /// <typeparam name="T">比較する値の型</typeparam>
        /// <param name="arr">対象の配列（※ソート済みであること）</param>
        /// <param name="value">検索する値</param>
        /// <returns>指定した値より大きい先頭のインデクス</returns>
        public static int UpperBound<T>(T[] arr, T value)
        {
            return UpperBound(arr, 0, arr.Length, value, Comparer<T>.Default);
        }

        public static IEnumerable<TResult> SelectNotNull<TSource, TResult>(this IEnumerable<TSource> source,
            Func<TSource, TResult> func)
            => source.Where(val => val != null).Select(func);

        public static IEnumerable<TSource> WhereNotNull<TSource>(this IEnumerable<TSource> source)
            => source.Where(val => val != null);

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static T[] ArrayOf<T>(params T[] arr) => arr;

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public static List<T> ListOf<T>(params T[] arr) => new List<T>(arr);

        public static IEnumerable<TResult> Repeat<TResult>(TResult value)
        {
            while (true) yield return value;
            // ReSharper disable once IteratorNeverReturns
        }

        public static IEnumerable<TResult> Repeat<TResult>(TResult value, int count)
            => Enumerable.Repeat(value, count);

        [SuppressMessage("ReSharper", "PossibleMultipleEnumeration")]
        public static IEnumerable<TResult> Repeat<TResult>(this IEnumerable<TResult> source, int count)
        {
            if (source == null) throw new ArgumentNullException(nameof(source));
            if (count < 0) throw new ArgumentOutOfRangeException(nameof(count));
            for (int i = 0; i < count; i++)
                foreach (var v in source)
                    yield return v;
        }

        [SuppressMessage("ReSharper", "PossibleMultipleEnumeration")]
        public static IEnumerable<TResult> Repeat<TResult>(this IEnumerable<TResult> source)
        {
            if (source == null) throw new ArgumentNullException(nameof(source));
            while (true)
                foreach (var v in source)
                    yield return v;
        }

        /// <summary>
        /// 文字の配列を文字列に変換します。
        /// </summary>
        /// <param name="source">文字の配列</param>
        /// <returns>変換した文字列</returns>
        public static string AsString(this IEnumerable<char> source) => new string(source.ToArray());

        /// <summary>
        /// <see cref="source"/> の累積和を返します。
        /// </summary>
        /// <returns><see cref="source"/> の累積和</returns>
        public static IEnumerable<long> CumSum(this IEnumerable<long> source)
        {
            long sum = 0;
            foreach (var item in source)
                yield return sum += item;
        }

        /// <summary>
        /// <see cref="source"/> の累積和を返します。
        /// </summary>
        /// <returns><see cref="source"/> の累積和</returns>
        public static IEnumerable<int> CumSum(this IEnumerable<int> source)
        {
            int sum = 0;
            foreach (var item in source)
                yield return sum += item;
        }

        /// <summary>
        /// <see cref="value"/>が l以上 r未満の範囲に含まれているかを返します。
        /// </summary>
        /// <typeparam name="T">要素の型</typeparam>
        /// <param name="value">判定する値</param>
        /// <param name="l">下限の値 (含まれる)</param>
        /// <param name="r">上限の値 (含まれない)</param>
        /// <returns><see cref="value"/> が指定した範囲に含まれているか</returns>
        public static bool IsIn<T>(this T value, T l, T r)
            where T : IComparable<T>
        {
            if (l.CompareTo(r) > 0) throw new ArgumentException();
            return l.CompareTo(value) <= 0 && value.CompareTo(r) < 0;
        }

        /// <summary>
        /// <see cref="start"/> 以上 <see cref="end"/> 未満の値を <see cref="step"/> ずつ増やした結果を列挙します。
        /// </summary>
        /// <param name="start">値の下限 (含まれる)</param>
        /// <param name="end">値の上限 (含まれない)</param>
        /// <param name="step">1要素ごとに増やす値</param>
        /// <returns>範囲の結果</returns>
        public static IEnumerable<int> Range(int start, int end, int step = 1)
        {
            for (var i = start; i < end; i += step) yield return i;
        }

        /// <summary>
        /// 0 以上 <see cref="end"/> 未満の値を 1 ずつ増やした結果を列挙します。
        /// </summary>
        /// <param name="end">値の上限 (含まれない)</param>
        /// <returns>範囲の結果</returns>
        public static IEnumerable<int> Range(int end) => Range(0, end);

        /// <summary>
        /// <see cref="start"/> 以上 <see cref="end"/> 未満の値を <see cref="step"/> ずつ増やした結果を逆順に列挙します。
        /// </summary>
        /// <param name="start">値の下限 (含まれる)</param>
        /// <param name="end">値の上限 (含まれない)</param>
        /// <param name="step">1要素ごとに増やす値</param>
        /// <returns>範囲の結果</returns>
        public static IEnumerable<int> RangeReverse(int start, int end, int step = 1)
        {
            for (var i = end - 1; i >= start; i -= step) yield return i;
        }

        /// <summary>
        /// 0 以上 <see cref="end"/> 未満の値を 1 ずつ増やした結果を逆順に列挙します。
        /// </summary>
        /// <param name="end">値の上限 (含まれない)</param>
        /// <returns>範囲の結果</returns>
        public static IEnumerable<int> RangeReverse(int end) => RangeReverse(0, end);


        /// <summary>
        /// 指定した配列をコピーして昇順ソートします。（非破壊的）
        /// </summary>
        /// <typeparam name="T">ソートする配列の型</typeparam>
        /// <param name="arr">ソートする配列</param>
        /// <returns>ソートされた配列</returns>
        public static T[] Sort<T>(this T[] arr)
        {
            var array = new T[arr.Length];
            arr.CopyTo(array, 0);
            Array.Sort(array);
            return array;
        }

        /// <summary>
        /// 指定した配列をコピーして降順ソートします。（非破壊的）
        /// </summary>
        /// <typeparam name="T">ソートする配列の型</typeparam>
        /// <param name="arr">ソートする配列</param>
        /// <returns>ソートされた配列</returns>
        public static T[] SortDescending<T>(this T[] arr)
        {
            var array = new T[arr.Length];
            arr.CopyTo(array, 0);
            Array.Sort(array);
            Array.Reverse(array);
            return array;
        }

        public static double Log2(double x) => Log(x, 2);

        public static bool chmin<T>(ref T a, T b) where T : IComparable<T>
        {
            if (a.CompareTo(b) > 0)
            {
                a = b;
                return true;
            }

            return false;
        }

        public static bool chmax<T>(ref T a, T b) where T : IComparable<T>
        {
            if (a.CompareTo(b) < 0)
            {
                a = b;
                return true;
            }

            return false;
        }

        public static T Min<T>(params T[] col) => col.Min();
        public static T Max<T>(params T[] col) => col.Max();


        /// <summary>
        /// 要素数 (a, b) の、defaultValue で満たされたジャグ配列を作成します。
        /// </summary>
        /// <typeparam name="T">配列の型</typeparam>
        /// <param name="a">1次元の要素数</param>
        /// <param name="b">2次元の要素数</param>
        /// <param name="defaultValue">デフォルト値</param>
        /// <returns>指定した条件で初期化された配列</returns>
        public static T[][] JaggedArray2D<T>(int a, int b, T defaultValue = default(T))
        {
            var ret = new T[a][];
            for (int i = 0; i < a; i++)
            {
                ret[i] = Enumerable.Repeat(defaultValue, b).ToArray();
            }

            return ret;
        }

        /// <summary>
        /// 要素数 (a, b) の，defaultValue で満たされた二次元配列を作成します。
        /// </summary>
        /// <param name="a">1次元の要素数</param>
        /// <param name="b">2次元の要素数</param>
        /// <param name="defaultValue">デフォルト値</param>
        /// <typeparam name="T">配列の型</typeparam>
        public static T[,] Array2D<T>(int a, int b, T defaultValue = default(T))
        {
            var ret = new T[a, b];
            for (int i = 0; i < a; i++)
            for (int j = 0; j < b; j++)
                ret[i, j] = defaultValue;
            return ret;
        }

        /// <summary>
        /// ジャグ配列を2次元配列に変換します。配列の各要素の長さがすべて同じである必要があります。
        /// </summary>
        /// <param name="array">ジャグ配列</param>
        /// <typeparam name="T">二次元配列</typeparam>
        public static T[,] To2DArray<T>(this T[][] array)
        {
            if (!array.Any()) return new T[0, 0];

            int len = array[0].Length;
            if (array.Any(x => x.Length != len))
                throw new ArgumentException("array の各要素の長さが異なります。", nameof(array));

            var ret = new T[array.Length, len];
            for (int i = 0; i < array.Length; i++)
            {
                for (int j = 0; j < len; j++)
                {
                    ret[i, j] = array[i][j];
                }
            }

            return ret;
        }

//        public static vector<T> ToVector<T>(this IEnumerable<T> source) => new vector<T>(source);
    }

    public static class Input
    {
        private const char _separator = ' ';
        private static readonly Queue<string> _input = new Queue<string>();
        private static readonly StreamReader sr =
#if FILE
            new StreamReader("in.txt");
#else
            new StreamReader(Console.OpenStandardInput());
#endif

        public static string ReadLine => sr.ReadLine();
        public static string ReadStr => Read;

        public static string Read
        {
            get
            {
                if (_input.Count != 0) return _input.Dequeue();

                // ReSharper disable once PossibleNullReferenceException
                var tmp = sr.ReadLine().Split(_separator);
                foreach (var val in tmp)
                {
                    _input.Enqueue(val);
                }

                return _input.Dequeue();
            }
        }

        public static int ReadInt => int.Parse(Read);
        public static long ReadLong => long.Parse(Read);
        public static double ReadDouble => double.Parse(Read);
        public static string[] StrArray() => ReadLine.Split(' ');
        public static int[] IntArray() => ReadLine.Split(' ').Select(int.Parse).ToArray();
        public static long[] LongArray() => ReadLine.Split(' ').Select(long.Parse).ToArray();

        public static string[] StrArray(int n)
        {
            var ret = new string[n];
            for (long i = 0; i < n; ++i) ret[i] = Read;
            return ret;
        }

        public static int[] IntArray(int n, int offset = 0, bool sorted = false)
        {
            var ret = StrArray(n).Select(x => int.Parse(x) + offset).ToArray();
            if (sorted) Array.Sort(ret);
            return ret;
        }

        public static long[] LongArray(int n, long offset = 0, bool sorted = false)
        {
            var ret = StrArray(n).Select(x => long.Parse(x) + offset).ToArray();
            if (sorted) Array.Sort(ret);
            return ret;
        }

        public static string[,] Str2DArray(int n, int m)
        {
            var ret = new string[n, m];
            for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
                ret[i, j] = ReadStr;

            return ret;
        }

        public static int[,] Int2DArray(int n, int m, int offset = 0)
        {
            var ret = new int[n, m];
            for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
                ret[i, j] = ReadInt + offset;
            return ret;
        }

        public static long[,] Long2DArray(int n, int m, long offset = 0)
        {
            var ret = new long[n, m];
            for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
                ret[i, j] = ReadLong + offset;
            return ret;
        }

        public static Tuple<string[], string[]> StrArrays2(int n)
        {
            var ret1 = new string[n];
            var ret2 = new string[n];
            for (int i = 0; i < n; i++)
            {
                ret1[i] = ReadStr;
                ret2[i] = ReadStr;
            }

            return Tuple.Create(ret1, ret2);
        }

        public static Tuple<int[], int[]> IntArrays2(int n, int offset1 = 0, int offset2 = 0)
        {
            var ret1 = new int[n];
            var ret2 = new int[n];
            for (int i = 0; i < n; i++)
            {
                ret1[i] = ReadInt + offset1;
                ret2[i] = ReadInt + offset2;
            }

            return Tuple.Create(ret1, ret2);
        }

        public static Tuple<long[], long[]> LongArrays2(int n, long offset1 = 0, long offset2 = 0)
        {
            var ret1 = new long[n];
            var ret2 = new long[n];
            for (int i = 0; i < n; i++)
            {
                ret1[i] = ReadLong + offset1;
                ret2[i] = ReadLong + offset2;
            }

            return Tuple.Create(ret1, ret2);
        }

        public static Tuple<string[], string[], string[]> StrArrays3(int n)
        {
            var ret1 = new string[n];
            var ret2 = new string[n];
            var ret3 = new string[n];
            for (int i = 0; i < n; i++)
            {
                ret1[i] = ReadStr;
                ret2[i] = ReadStr;
            }

            return Tuple.Create(ret1, ret2, ret3);
        }

        public static Tuple<int[], int[], int[]> IntArrays3(int n, int offset1 = 0, int offset2 = 0, int offset3 = 0)
        {
            var ret1 = new int[n];
            var ret2 = new int[n];
            var ret3 = new int[n];
            for (int i = 0; i < n; i++)
            {
                ret1[i] = ReadInt + offset1;
                ret2[i] = ReadInt + offset2;
                ret3[i] = ReadInt + offset3;
            }

            return Tuple.Create(ret1, ret2, ret3);
        }

        public static Tuple<long[], long[], long[]> LongArrays3(int n, long offset1 = 0, long offset2 = 0,
            long offset3 = 0)
        {
            var ret1 = new long[n];
            var ret2 = new long[n];
            var ret3 = new long[n];
            for (int i = 0; i < n; i++)
            {
                ret1[i] = ReadLong + offset1;
                ret2[i] = ReadLong + offset2;
                ret3[i] = ReadLong + offset3;
            }

            return Tuple.Create(ret1, ret2, ret3);
        }

        private static bool TypeEquals<T, U>() => typeof(T) == typeof(U);
        private static T ChangeType<T, U>(U a) => (T) System.Convert.ChangeType(a, typeof(T));

        private static T Convert<T>(string s) => TypeEquals<T, int>() ? ChangeType<T, int>(int.Parse(s))
            : TypeEquals<T, long>() ? ChangeType<T, long>(long.Parse(s))
            : TypeEquals<T, double>() ? ChangeType<T, double>(double.Parse(s))
            : TypeEquals<T, char>() ? ChangeType<T, char>(s[0])
            : ChangeType<T, string>(s);

        public static bool In<T>(out T a)
        {
            try
            {
                a = Convert<T>(Read);
                return true;
            }
            catch
            {
                a = default(T);
                return false;
            }
        }

        public static bool In<T, U>(out T a, out U b)
        {
            try
            {
                var ar = StrArray(2);
                a = Convert<T>(ar[0]);
                b = Convert<U>(ar[1]);
                return true;
            }
            catch
            {
                a = default(T);
                b = default(U);
                return false;
            }
        }

        public static bool In<T, U, V>(out T a, out U b, out V c)
        {
            try
            {
                var ar = StrArray(3);
                a = Convert<T>(ar[0]);
                b = Convert<U>(ar[1]);
                c = Convert<V>(ar[2]);
                return true;
            }
            catch
            {
                a = default(T);
                b = default(U);
                c = default(V);
                return false;
            }
        }

        public static bool In<T, U, V, W>(out T a, out U b, out V c, out W d)
        {
            try
            {
                var ar = StrArray(4);
                a = Convert<T>(ar[0]);
                b = Convert<U>(ar[1]);
                c = Convert<V>(ar[2]);
                d = Convert<W>(ar[3]);
                return true;
            }
            catch
            {
                a = default(T);
                b = default(U);
                c = default(V);
                d = default(W);
                return false;
            }
        }

        public static bool In<T, U, V, W, X>(out T a, out U b, out V c, out W d, out X e)
        {
            try
            {
                var ar = StrArray(5);
                a = Convert<T>(ar[0]);
                b = Convert<U>(ar[1]);
                c = Convert<V>(ar[2]);
                d = Convert<W>(ar[3]);
                e = Convert<X>(ar[4]);
                return true;
            }
            catch
            {
                a = default(T);
                b = default(U);
                c = default(V);
                d = default(W);
                e = default(X);
                return false;
            }
        }
    }

    public static class Output
    {
        public static void print<T>(T t) => Console.WriteLine(t);
        public static void print(params object[] o) => Console.WriteLine(o.Join(" "));

        public static void PrintBool(bool val, string yes = "Yes", string no = "No")
            => Console.WriteLine(val ? yes : no);

        public static void PrintYn(bool val) => PrintBool(val);
        public static void PrintYN(bool val) => PrintBool(val, "YES", "NO");
        public static void PrintPossible(bool val) => PrintBool(val, "Possible", "Impossible");
        public static void PrintYay(bool val) => PrintBool(val, "Yay!", ":(");

        public static void PrintDebug(params object[] args)
            => Console.Error.WriteLine(string.Join(" ", args));

        /// <summary>
        /// setter で設定された値を標準出力に出力します。
        /// </summary>
        public static object cout { set { Console.WriteLine(value); } }

        /// <summary>
        /// Local環境のみ，setter で設定された値を標準出力に出力します。
        /// </summary>
        public static object dout
        {
            set
            {
#if LOCAL
                Console.WriteLine(value);
#endif
            }
        }

        /// <summary>
        /// setter で設定された値を標準エラー出力に出力します。
        /// </summary>
        public static object cerr { set { Console.Error.WriteLine(value); } }

        public const string endl = "\n";
    }

    public class Program
    {
        public static void Main(string[] args)
        {
            var sw = new StreamWriter(Console.OpenStandardOutput()) {AutoFlush = false};
            Console.SetOut(sw);
            new Solver().Main();

            Console.Out.Flush();
            Console.Read();
        }
    }

    [DebuggerDisplay("({first}, {second})")]
    public class Pair<T1, T2> : IComparable<Pair<T1, T2>>, IEquatable<Pair<T1, T2>>
        where T1 : IComparable<T1>
        where T2 : IComparable<T2>
    {
        public Pair(T1 first, T2 second)
        {
            this.first = first;
            this.second = second;
        }

        public T1 first;
        public T2 second;

        public int CompareTo(Pair<T1, T2> other)
        {
            if (ReferenceEquals(this, other)) return 0;
            if (ReferenceEquals(null, other)) return 1;
            var firstComparison = first.CompareTo(other.first);
            return firstComparison != 0 ? firstComparison : second.CompareTo(other.second);
        }

        public override string ToString() => $"({first}, {second})";

        public bool Equals(Pair<T1, T2> other)
        {
            if (ReferenceEquals(null, other)) return false;
            if (ReferenceEquals(this, other)) return true;
            return EqualityComparer<T1>.Default.Equals(first, other.first) &&
                   EqualityComparer<T2>.Default.Equals(second, other.second);
        }

        public override bool Equals(object obj)
        {
            if (ReferenceEquals(null, obj)) return false;
            if (ReferenceEquals(this, obj)) return true;
            return obj.GetType() == GetType() && Equals((Pair<T1, T2>) obj);
        }

        public override int GetHashCode()
        {
            unchecked
            {
                return (EqualityComparer<T1>.Default.GetHashCode(first) * 397) ^
                       EqualityComparer<T2>.Default.GetHashCode(second);
            }
        }
    }

    #endregion
}