백준 1018번 - 체스판 다시 칠하기

score = []
chess = []

n, m = map(int, input().split())

for _ in range(n):
  chess.append(input())

for x in range(n-7):
  for y in range(m-7):
    W_start = 0
    B_start = 0
    for i in range(x, x+8):
      for j in range(y, y+8):
        if (i+j) % 2 == 0:
          if chess[i][j] != "W":
            W_start += 1
          else:
            B_start += 1
        else:
          if chess[i][j] != "W":
            B_start += 1
          else:
            W_start += 1
    score.append(B_start)
    score.append(W_start)

print(min(score))