Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
C = list(map(lambda x: int(x) - 1, input().split()))
D = list(map(lambda x: int(x) - 1, input().split()))
S = [input() for _ in range(H)]
toGo = [[False if i != C[0] or j != C[1] else True for j in range(W)] for i in range(H)]
queue = [C]
ans = 0
 
while True:
    tmp = queue.pop()
    dfs = [tmp]
 
    while len(dfs):
        a = dfs.pop()
        for move in [[0, 1], [0, -1], [1, 0], [-1, 0]]:
            hh, ww = a[0] + move[0], a[1] + move[1]
            if hh >= H or hh < 0 or ww >= W or ww < 0:
                continue
 
            if not toGo[hh][ww] and S[hh][ww] == '.':
                toGo[hh][ww] = True
                dfs.append([hh, ww])
 
    if toGo[D[0]][D[1]]:
        break
 
    flag = True
    if not len(queue):
        ttogo = [[toGo[i][j] for j in range(W)] for i in range(H)]
        ans += 1
        for i in range(H):
            for j in range(W):
                if not toGo[i][j] and S[i][j] == ".":
                    t = False
                    for ii in range(-2, 3):
                        for jj in range(-2, 3):
                            hh, ww = i + ii, j + jj
                            if hh >= H or hh < 0 or ww >= W or ww < 0:
                                continue
 
                            if toGo[hh][ww]:
                                ttogo[i][j] = True
                                flag, t = False, True
                                queue.append([i, j])
                                break
                        if t:
                            break
        toGo = ttogo
        if flag:
            print(-1)
            exit()
 
print(ans)

Fixed submission:
H, W = map(int, input().split())
C = list(map(lambda x: int(x) - 1, input().split()))
D = list(map(lambda x: int(x) - 1, input().split()))
S = [input() for _ in range(H)]
toGo = [[False if i != C[0] or j != C[1] else True for j in range(W)] for i in range(H)]
queue, mahou = [C], [C]
ans = 0

while True:
    tmp = queue.pop()
    mahou.append(tmp)
    dfs = [tmp]

    while len(dfs):
        a = dfs.pop()
        for move in [[0, 1], [0, -1], [1, 0], [-1, 0]]:
            hh, ww = a[0] + move[0], a[1] + move[1]
            if hh >= H or hh < 0 or ww >= W or ww < 0:
                continue

            if not toGo[hh][ww] and S[hh][ww] == '.':
                toGo[hh][ww] = True
                dfs.append([hh, ww])
                mahou.append([hh, ww])

    if toGo[D[0]][D[1]]:
        break

    flag = True
    if not len(queue):
        ans += 1
        for k in mahou:
            for i in range(-2, 3):
                for j in range(-2, 3):
                    h, w = i + k[0], j + k[1]
                    if h >= H or h < 0 or w >= W or w < 0:
                        continue

                    if not toGo[h][w] and S[h][w] == '.':
                        flag = False
                        toGo[h][w] = True
                        queue.append([h, w])
        mahou = []

        if flag:
            print(-1)
            exit()

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
C = list(map(lambda x: int(x) - 1, input().split()))
D = list(map(lambda x: int(x) - 1, input().split()))
S = [input() for _ in range(H)]
toGo = [[False if i != C[0] or j != C[1] else True for j in range(W)] for i in range(H)]
queue = [C]
ans = 0

while True:
    tmp = queue.pop()
    dfs = [tmp]

    while len(dfs):
        a = dfs.pop()
        for move in [[0, 1], [0, -1], [1, 0], [-1, 0]]:
            hh, ww = a[0] + move[0], a[1] + move[1]
            if hh >= H or hh < 0 or ww >= W or ww < 0:
                continue

            if not toGo[hh][ww] and S[hh][ww] == '.':
                toGo[hh][ww] = True
                dfs.append([hh, ww])

    if toGo[D[0]][D[1]]:
        break

    flag = True
    if not len(queue):
        ttogo = [[toGo[i][j] for j in range(W)] for i in range(H)]
        ans += 1
        for i in range(H):
            for j in range(W):
                if not toGo[i][j] and S[i][j] == ".":
                    t = False
                    for ii in range(-2, 3):
                        for jj in range(-2, 3):
                            hh, ww = i + ii, j + jj
                            if hh >= H or hh < 0 or ww >= W or ww < 0:
                                continue

                            if toGo[hh][ww]:
                                ttogo[i][j] = True
                                flag, t = False, True
                                queue.append([i, j])
                                break
                        if t:
                            break
        toGo = ttogo
        if flag:
            print(-1)
            exit()

print(ans)


Fixed submission:
H, W = map(int, input().split())
C = list(map(lambda x: int(x) - 1, input().split()))
D = list(map(lambda x: int(x) - 1, input().split()))
S = [input() for _ in range(H)]
toGo = [[False if i != C[0] or j != C[1] else True for j in range(W)] for i in range(H)]
queue, mahou = [C], [C]
ans = 0

while True:
    tmp = queue.pop()
    mahou.append(tmp)
    dfs = [tmp]

    while len(dfs):
        a = dfs.pop()
        for move in [[0, 1], [0, -1], [1, 0], [-1, 0]]:
            hh, ww = a[0] + move[0], a[1] + move[1]
            if hh >= H or hh < 0 or ww >= W or ww < 0:
                continue

            if not toGo[hh][ww] and S[hh][ww] == '.':
                toGo[hh][ww] = True
                dfs.append([hh, ww])
                mahou.append([hh, ww])

    if toGo[D[0]][D[1]]:
        break

    flag = True
    if not len(queue):
        ans += 1
        for k in mahou:
            for i in range(-2, 3):
                for j in range(-2, 3):
                    h, w = i + k[0], j + k[1]
                    if h >= H or h < 0 or w >= W or w < 0:
                        continue

                    if not toGo[h][w] and S[h][w] == '.':
                        flag = False
                        toGo[h][w] = True
                        queue.append([h, w])
        mahou = []

        if flag:
            print(-1)
            exit()

print(ans)