Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
import sys
def input(): return sys.stdin.readline().rstrip()


class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())


def main():
    h, w = map(int, input().split())
    s = [list(input()) for i in range(h)]
    uf = UnionFind(h*w)
    for i in range(h):
        for j in range(w):
            if i != h-1:
                if s[i][j] != s[i+1][j]:
                    uf.union((i*w)+j, (i*w)+j+w)
            if j != w-1:
                if s[i][j] != s[i][j+1]:
                    uf.union((i*w)+j, (i*w)+j+1)
    ans=0
    for item in uf.all_group_members().values():
        A=0
        B=0
        for grid in item:
            i,j=divmod(grid,w)
            if s[i][j]=='.':
                A+=1
            else:
                B+=1
        ans+=A*B
    print(ans)


if __name__ == '__main__':
    main()

Fixed submission:
import sys
def input(): return sys.stdin.readline().rstrip()
from collections import defaultdict

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        self.all_group_member=defaultdict(list)
        for i in range(self.n):
            self.all_group_member[self.find(i)].append(i)
        return self.all_group_member

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())


def main():
    h, w = map(int, input().split())
    s = [list(input()) for i in range(h)]
    uf = UnionFind(h*w)
    for i in range(h):
        for j in range(w):
            if i != h-1:
                if s[i][j] != s[i+1][j]:
                    uf.union((i*w)+j, (i*w)+j+w)
            if j != w-1:
                if s[i][j] != s[i][j+1]:
                    uf.union((i*w)+j, (i*w)+j+1)
    ans=0
    for item in uf.all_group_members().values():
        A=0
        B=0
        for grid in item:
            i,j=divmod(grid,w)
            if s[i][j]=='.':
                A+=1
            else:
                B+=1
        ans+=A*B
    print(ans)
 
 
if __name__ == '__main__':
    main()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
import sys
from collections import deque
def input(): return sys.stdin.readline().rstrip()


class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        return {r: self.members(r) for r in self.roots()}

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())


def main():
    h, w = map(int, input().split())
    s = [list(input()) for i in range(h)]
    uf = UnionFind(h*w)
    for i in range(h):
        for j in range(w):
            if i != h-1:
                if s[i][j] != s[i+1][j]:
                    uf.union((i*w)+j, (i*w)+j+w)
            if j != w-1:
                if s[i][j] != s[i][j+1]:
                    uf.union((i*w)+j, (i*w)+j+1)
    ans=0
    for item in uf.all_group_members().values():
        A=0
        B=0
        for grid in item:
            i,j=divmod(grid,w)
            if s[i][j]=='.':
                A+=1
            else:
                B+=1
        ans+=A*B
    print(ans)


if __name__ == '__main__':
    main()

Fixed submission:
import sys
def input(): return sys.stdin.readline().rstrip()
from collections import defaultdict

class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        self.all_group_member=defaultdict(list)
        for i in range(self.n):
            self.all_group_member[self.find(i)].append(i)
        return self.all_group_member

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())


def main():
    h, w = map(int, input().split())
    s = [list(input()) for i in range(h)]
    uf = UnionFind(h*w)
    for i in range(h):
        for j in range(w):
            if i != h-1:
                if s[i][j] != s[i+1][j]:
                    uf.union((i*w)+j, (i*w)+j+w)
            if j != w-1:
                if s[i][j] != s[i][j+1]:
                    uf.union((i*w)+j, (i*w)+j+1)
    ans=0
    for item in uf.all_group_members().values():
        A=0
        B=0
        for grid in item:
            i,j=divmod(grid,w)
            if s[i][j]=='.':
                A+=1
            else:
                B+=1
        ans+=A*B
    print(ans)
 
 
if __name__ == '__main__':
    main()