def solution(m, n, board):

answer = 0

board = [list(i) for i in board]

flag = False

while not flag:

visited = [[False for _ in range(n)] for _ in range(m)]

for row in range(m - 1):

for col in range(n - 1):

if (board[row][col] == board[row][col + 1] == board[row + 1][col] == board[row + 1][col + 1]) and \

board[row][col] != '':

visited[row][col] = visited[row][col + 1] = visited[row + 1][col] = visited[row + 1][col + 1] = True

cnt = 0

for v in visited:

cnt += v.count(True)

answer += cnt

new_board = [[board[row][col] if visited[row][col] == False else '' for col in range(n)] for row in range(m)]

new_board = new_board[::-1]

for row in range(m):

for col in range(n):

if new_board[row][col] == '':

for up in range(row, m):

if new_board[up][col]:

new_board[row][col] = new_board[up][col]

new_board[up][col] = ''

break

new_board = new_board[::-1]

if board == new_board:

flag = True

else:

board = new_board

return answer