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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func getScanner(fp *os.File) *bufio.Scanner {
	scanner := bufio.NewScanner(fp)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 500001), 500000)
	return scanner
}

func getNextString(scanner *bufio.Scanner) string {
	scanner.Scan()
	return scanner.Text()
}

func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}

func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}

func getNextUint64(scanner *bufio.Scanner) uint64 {
	i, _ := strconv.ParseUint(getNextString(scanner), 10, 64)
	return i
}

func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}

func main() {
	fp := os.Stdin
	wfp := os.Stdout

	if len(os.Args) > 1 {
		fp, _ = os.Open(os.Args[1])
		if len(os.Args) > 2 {
			wfp, _ = os.Create(os.Args[2])
		}
	}

	scanner := getScanner(fp)
	writer := bufio.NewWriter(wfp)

	h := getNextInt(scanner)
	w := getNextInt(scanner)
	grid := make([]string, h)

	for i := 0; i < h; i++ {
		grid[i] = getNextString(scanner)
	}

	cnt := h * w
	color := make([]int, cnt)
	for i := 0; i < cnt; i++ {
		color[i] = i
	}

	for y := 0; y < h; y++ {
		for x := 0; x < w; x++ {
			if y > 0 && grid[y][x] != grid[y-1][x] {
				r1 := root(y*w+x, color)
				r2 := root((y-1)*w+x, color)
				if r1 != r2 {
					color[r2] = r1
				}
			}
			if x > 0 && grid[y][x] != grid[y][x-1] {
				r1 := root(y*w+x, color)
				r2 := root(y*w+x-1, color)
				if r1 != r2 {
					color[r2] = r1
				}
			}
		}
	}

	sum := makeInts(cnt, 2)
	ans := 0
	for y := 0; y < h; y++ {
		for x := 0; x < w; x++ {
			r := root(y*w+x, color)
			if grid[y][x] == '#' {
				sum[r][0]++
				continue
			}
			sum[r][1]++
		}
	}

	for i := 0; i < cnt; i++ {
		ans += sum[i][0] * sum[i][1]
	}

	fmt.Fprintln(writer, ans)

	writer.Flush()
}

func makeInts(h, w int) [][]int {
	index := make([][]int, h, h)
	data := make([]int, h*w, h*w)
	for i := 0; i < h; i++ {
		index[i] = data[i*w : (i+1)*w]
	}
	return index
}

func root(i int, color []int) int {
	if i == color[i] {
		return i
	}
	color[i] = root(color[i], color)
	return color[i]
}