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

matched = True

while matched:

# 1) 일치 여부 판별

matched = []

for i in range(m - 1):

for j in range(n - 1):

if board[i][j] == \

board[i][j + 1] == \

board[i + 1][j + 1] == \

board[i + 1][j] != '#':

matched.append([i, j])

# 2) 일치한 위치 삭제

for i, j in matched:

board[i][j] = board[i][j + 1] = board[i + 1][j + 1] = board[i + 1][j] = '#'

# 3) 빈공간 블럭 처리

for _ in range(m):

for i in range(m - 1):

for j in range(n):

if board[i + 1][j] == '#':

board[i + 1][j], board[i][j] = board[i][j], '#'