Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
from itertools import product


def bfs(x, y):
    dist = [[10 ** 9] * w for _ in range(h)]
    dist[y][x] = 0
    que = deque([(x, y)])
    move = product(range(-2, 3), repeat=2)
    near = [(dx, dy, (abs(dx) + abs(dy) >= 2)) for dx, dy in move]

    while len(que) > 0:
        x, y = que.popleft()
        if (x, y) == (Dw - 1, Dh - 1):
            return dist[y][x]

        for dx, dy, cnt in near:
            i, j = x + dx, y + dy
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] + cnt and s[j][i] == '.'):
                dist[j][i] = dist[y][x] + cnt
                if cnt == 0:
                    que.appendleft((i, j))
                elif cnt == 1:
                    que.append((i, j))
    return -1


h, w = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())
s = [input() for _ in range(h)]

print(bfs(Cw - 1, Ch - 1))


Fixed submission:
from collections import deque
from itertools import product


def bfs(S):
    x, y = S
    dist = [[10 ** 9] * w for _ in range(h)]
    dist[y][x] = 0
    que = deque([S])

    while len(que) > 0:
        x, y = que.popleft()
        near_a = [(x + 1, y), (x - 1, y), (x, y + 1), (x, y - 1)]
        num = product([-2, -1, 0, 1, 2], repeat=2)
        near_b = [(x + dx, y + dy) for dx, dy in num]

        for i, j in near_a:
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] and s[j][i] == '.'):
                dist[j][i] = dist[y][x]
                que.appendleft((i, j))
        for i, j in near_b:
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] + 1 and s[j][i] == '.'):
                dist[j][i] = dist[y][x] + 1
                que.append((i, j))
    return dist


h, w = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())
s = [input() for _ in range(h)]

ans = bfs((Cw - 1, Ch - 1))[Dh - 1][Dw - 1]
print(-1 if ans == 10 ** 9 else ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
from itertools import product


def bfs(x, y):
    dist = [[10 ** 9] * w for _ in range(h)]
    dist[y][x] = 0
    que = deque([(x, y)])

    while len(que) > 0:
        x, y = que.popleft()
        if (x, y) == (Dw - 1, Dh - 1):
            return dist[y][x]

        for i, j in product(range(-2, 3), repeat=2):
            cnt = (abs(i) + abs(j) >= 2)
            i, j = x + i, y + j
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] + cnt and s[j][i] == '.'):
                dist[j][i] = dist[y][x] + cnt
                if cnt == 0:
                    que.appendleft((i, j))
                elif cnt == 1:
                    que.append((i, j))
    return -1


h, w = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())
s = [input() for _ in range(h)]

print(bfs(Cw - 1, Ch - 1))


Fixed submission:
from collections import deque
from itertools import product


def bfs(S):
    x, y = S
    dist = [[10 ** 9] * w for _ in range(h)]
    dist[y][x] = 0
    que = deque([S])

    while len(que) > 0:
        x, y = que.popleft()
        near_a = [(x + 1, y), (x - 1, y), (x, y + 1), (x, y - 1)]
        num = product([-2, -1, 0, 1, 2], repeat=2)
        near_b = [(x + dx, y + dy) for dx, dy in num]

        for i, j in near_a:
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] and s[j][i] == '.'):
                dist[j][i] = dist[y][x]
                que.appendleft((i, j))
        for i, j in near_b:
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] + 1 and s[j][i] == '.'):
                dist[j][i] = dist[y][x] + 1
                que.append((i, j))
    return dist


h, w = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())
s = [input() for _ in range(h)]

ans = bfs((Cw - 1, Ch - 1))[Dh - 1][Dw - 1]
print(-1 if ans == 10 ** 9 else ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
from itertools import product


def bfs(x, y):
    dist = [[10 ** 9] * w for _ in range(h)]
    dist[y][x] = 0
    for i, si in enumerate(s):
        for j, sij in enumerate(si):
            if sij=='#':
                dist[j][i] = -1
    que = deque([(x, y)])

    while len(que) > 0:
        x, y = que.popleft()
        near_a = [(x + 1, y), (x - 1, y), (x, y + 1), (x, y - 1)]
        num = product([-2, -1, 0, 1, 2], repeat=2)
        near_b = [(x + dx, y + dy) for dx, dy in num]

        for cnt, l in enumerate((near_a, near_b)):
            for i, j in l:
                if (0 <= i < w and 0 <= j < h and
                        dist[j][i] > dist[y][x] + cnt and s[j][i] == '.'):
                    dist[j][i] = dist[y][x] + cnt
                    if cnt == 0:
                        que.appendleft((i, j))
                    elif cnt == 1:
                        que.append((i, j))
    return dist


h, w = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())
s = [input() for _ in range(h)]

ans = bfs(Cw - 1, Ch - 1)[Dh - 1][Dw - 1]
print(-1 if ans == 10 ** 9 else ans)


Fixed submission:
from collections import deque
from itertools import product


def bfs(S):
    x, y = S
    dist = [[10 ** 9] * w for _ in range(h)]
    dist[y][x] = 0
    que = deque([S])

    while len(que) > 0:
        x, y = que.popleft()
        near_a = [(x + 1, y), (x - 1, y), (x, y + 1), (x, y - 1)]
        num = product([-2, -1, 0, 1, 2], repeat=2)
        near_b = [(x + dx, y + dy) for dx, dy in num]

        for i, j in near_a:
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] and s[j][i] == '.'):
                dist[j][i] = dist[y][x]
                que.appendleft((i, j))
        for i, j in near_b:
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] + 1 and s[j][i] == '.'):
                dist[j][i] = dist[y][x] + 1
                que.append((i, j))
    return dist


h, w = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())
s = [input() for _ in range(h)]

ans = bfs((Cw - 1, Ch - 1))[Dh - 1][Dw - 1]
print(-1 if ans == 10 ** 9 else ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
from itertools import product


def bfs(S):
    x, y = S
    dist = [[10 ** 9] * w for _ in range(h)]
    dist[y][x] = 0
    que = deque([S])

    while len(que) > 0:
        x, y = que.popleft()
        near_a = [(x + 1, y), (x - 1, y), (x, y + 1), (x, y - 1)]
        num = product([-2, -1, 0, 1, 2], repeat=2)
        near_b = [(x + dx, y + dy) for dx, dy in num]

        for i, j in near_a:
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] and s[j][i] == '.'):
                dist[j][i] = dist[y][x]
                que.append((i, j))
        for i, j in near_b:
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] + 1 and s[j][i] == '.'):
                dist[j][i] = dist[y][x] + 1
                que.append((i, j))
    return dist


h, w = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())
s = [input() for _ in range(h)]

ans = bfs((Cw - 1, Ch - 1))[Dh - 1][Dw - 1]
print(-1 if ans == 10 ** 9 else ans)


Fixed submission:
from collections import deque
from itertools import product


def bfs(S):
    x, y = S
    dist = [[10 ** 9] * w for _ in range(h)]
    dist[y][x] = 0
    que = deque([S])

    while len(que) > 0:
        x, y = que.popleft()
        near_a = [(x + 1, y), (x - 1, y), (x, y + 1), (x, y - 1)]
        num = product([-2, -1, 0, 1, 2], repeat=2)
        near_b = [(x + dx, y + dy) for dx, dy in num]

        for i, j in near_a:
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] and s[j][i] == '.'):
                dist[j][i] = dist[y][x]
                que.appendleft((i, j))
        for i, j in near_b:
            if (0 <= i < w and 0 <= j < h and
                    dist[j][i] > dist[y][x] + 1 and s[j][i] == '.'):
                dist[j][i] = dist[y][x] + 1
                que.append((i, j))
    return dist


h, w = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())
s = [input() for _ in range(h)]

ans = bfs((Cw - 1, Ch - 1))[Dh - 1][Dw - 1]
print(-1 if ans == 10 ** 9 else ans)