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 Rust (1.15.1) (judge verdict: Accepted)

use std::io::Read;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let h: usize = itr.next().unwrap().parse().unwrap();
    let w: usize = itr.next().unwrap().parse().unwrap();
    let s: Vec<Vec<char>> = (0..h)
        .map(|_| itr.next().unwrap().chars().collect())
        .collect();

    let mut ans: u64 = 0;
    let mut q = std::collections::VecDeque::new();
    let mut visit = vec![vec![false; w]; h];
    for i in 0..h {
        for j in 0..w {
            if !visit[i][j] && s[i][j] == '#' {
                visit[i][j] = true;
                q.push_back((i, j));
                let mut kuro: u64 = 1;
                let mut shiro: u64 = 0;
                while let Some((y, x)) = q.pop_front() {
                    for (dy, dx) in vec![(-1, 0), (1, 0), (0, -1), (0, 1)] {
                        let ny = ((y as isize) + dy) as usize;
                        let nx = ((x as isize) + dx) as usize;
                        if nx < w && ny < h && !visit[ny][nx] {
                            if s[ny][nx] == '.' && s[y][x] == '#' {
                                shiro += 1;
                                q.push_back((ny, nx));
                                visit[ny][nx] = true;
                            } else if s[ny][nx] == '#' && s[y][x] == '.' {
                                kuro += 1;
                                q.push_back((ny, nx));
                                visit[ny][nx] = true;
                            }
                        }
                    }
                }
                ans += shiro * kuro;
            }
        }
    }
    println!("{}", ans);
}