Problem:
Score : 300 points

Problem Statement

There is a grid with H rows and W columns, where each square is painted black or white.

You are given H strings S_1, S_2, ..., S_H, each of length W.
If the square at the i-th row from the top and the j-th column from the left is painted black, the j-th character in the string S_i is #; if that square is painted white, the j-th character in the string S_i is ..

Find the number of pairs of a black square c_1 and a white square c_2 that satisfy the following condition:

There is a path from the square c_1 to the square c_2 where we repeatedly move to a vertically or horizontally adjacent square through an alternating sequence of black and white squares: black, white, black, white...

Constraints

1 \leq H, W \leq 400

|S_i| = W (1 \leq i \leq H)

For each i (1 \leq i \leq H), the string S_i consists of characters # and ..

Input

Input is given from Standard Input in the following format:

H W
S_1
S_2
:
S_H

Output

Print the answer.

Sample Input 1

3 3
.#.
..#
#..

Sample Output 1

10

Some of the pairs satisfying the condition are ((1, 2), (3, 3)) and ((3, 1), (3, 2)), where (i, j) denotes the square at the i-th row from the top and the j-th column from the left.

Sample Input 2

2 4
....
....

Sample Output 2

0

Sample Input 3

4 3
###
###
...
###

Sample Output 3

6

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

using System;
using System.Collections.Generic;
using System.Linq;

namespace ASPC2019_C
{
    class Program
    {
        static char[][] S;
        static bool[,] isChecked = new bool[400, 400];
        static int[] xdir = new int[] { 0, 0, -1, 1 };
        static int[] ydir = new int[] { -1, 1, 0, 0 };

        static int cntb, cntw;
        static int H, W;

        static void Main(string[] args)
        {
            var HW = Console.ReadLine().Split().Select(int.Parse).ToArray();
            H = HW[0];
            W = HW[1];
            S = new char[H][];
            for (int i = 0; i < H; i++)
            {
                S[i] = Console.ReadLine().ToCharArray();
            }

            var startpoint = new List<Tuple<int, int>>();
            var endpoint = new List<Tuple<int, int>>();

            long sum = 0;
            for (int h = 0; h < H; h++)
            {
                for (int w = 0; w < W; w++)
                {
                    if (S[h][w] == '.' || isChecked[h, w]) continue;
                    cntb = 0;
                    cntw = 0;
                    DFS(h, w);
                    sum += cntb * cntw;
                }
            }

            Console.WriteLine(sum);
        }

        private static void DFS(int h, int w)
        {
            isChecked[h, w] = true;
            if (S[h][w] == '#') cntb++;
            else cntw++;

            for (int i = 0; i < xdir.Length; i++)
            {
                var neww = w + xdir[i];
                var newh = h + ydir[i];
                if (neww < 0 || neww >= W || newh < 0 || newh >= H) continue;
                if (S[newh][neww] == S[h][w]) continue;
                if (isChecked[newh, neww]) continue;
                DFS(newh, neww);
            }
        }
    }
}