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

H, W = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())

grid = []
for i in range(H):
    grid.append(input().rstrip())

d = deque()
d.append((Ch-1, Cw-1, 0))

memo = [[[False] * W for _ in range(H)] for _ in range(1000)]
memo[0][Ch-1][Cw-1] = True

searched = [[False] * W for _ in range(H)]

ans = -1

while d:
    h, w, c = d.popleft()

    if searched[h][w]:
        continue

    searched[h][w] = True

    if h == Dh-1 and w == Dw-1:
        ans = c
        break

    for i, j in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        if 0 <= h+i < H and 0 <= w+j < W:
            if grid[h+i][w+j] == '.':
                if not memo[c][h+i][w+j]:
                    memo[c][h+i][w+j] = True
                    d.appendleft((h+i, w+j, c))

    for i in range(-2, 3):
        for j in range(-2, 3):
            if 0 <= h+i < H and 0 <= w+j < W:
                if grid[h+i][w+j] == '.':
                    if not memo[c][h+i][w+j] and not memo[c+1][h+i][w+j] and not searched[h+i][w+j]:
                        memo[c+1][h+i][w+j] = True
                        d.append((h+i, w+j, c+1))

print(ans)


Fixed submission:
from collections import deque

H, W = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())

grid = []
for i in range(H):
    grid.append(input().rstrip())

d = deque()
d.append((Ch-1, Cw-1, 0))

memo = [[[False] * W for _ in range(H)] for _ in range(2)]
memo[0][Ch-1][Cw-1] = True

searched = [[False] * W for _ in range(H)]

ans = -1

while d:
    h, w, c = d.popleft()

    if searched[h][w]:
        continue

    searched[h][w] = True

    if h == Dh-1 and w == Dw-1:
        ans = c
        break

    for i, j in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        if 0 <= h+i < H and 0 <= w+j < W:
            if grid[h+i][w+j] == '.':
                if not memo[0][h+i][w+j] and not searched[h+i][w+j]:
                    memo[0][h+i][w+j] = True
                    d.appendleft((h+i, w+j, c))

    for i in range(-2, 3):
        for j in range(-2, 3):
            if 0 <= h+i < H and 0 <= w+j < W:
                if grid[h+i][w+j] == '.':
                    if not memo[0][h+i][w+j] and not memo[1][h+i][w+j] and not searched[h+i][w+j]:
                        memo[1][h+i][w+j] = True
                        d.append((h+i, w+j, c+1))

print(ans)

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

H, W = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())

grid = []
for i in range(H):
    grid.append(input().rstrip())

d = deque()
d.append((Ch-1, Cw-1, 0))

memo = [[[False] * W for _ in range(H)] for _ in range(1000)]
memo[0][Ch-1][Cw-1] = True

searched = [[False] * W for _ in range(H)]

ans = -1

while d:
    h, w, c = d.popleft()

    if searched[h][w]:
        continue

    searched[h][w] = True

    if h == Dh-1 and w == Dw-1:
        ans = c
        break

    for i, j in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        if 0 <= h+i < H and 0 <= w+j < W:
            if grid[h+i][w+j] == '.':
                if not memo[c][h+i][w+j]:
                    memo[c][h+i][w+j] = True
                    d.appendleft((h+i, w+j, c))

    for i in range(-2, 3):
        for j in range(-2, 3):
            if 0 <= h+i < H and 0 <= w+j < W:
                if grid[h+i][w+j] == '.':
                    if not memo[c][h+i][w+j] and not memo[c+1][h+i][w+j]:
                        memo[c+1][h+i][w+j] = True
                        d.append((h+i, w+j, c+1))

print(ans)


Fixed submission:
from collections import deque

H, W = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())

grid = []
for i in range(H):
    grid.append(input().rstrip())

d = deque()
d.append((Ch-1, Cw-1, 0))

memo = [[[False] * W for _ in range(H)] for _ in range(2)]
memo[0][Ch-1][Cw-1] = True

searched = [[False] * W for _ in range(H)]

ans = -1

while d:
    h, w, c = d.popleft()

    if searched[h][w]:
        continue

    searched[h][w] = True

    if h == Dh-1 and w == Dw-1:
        ans = c
        break

    for i, j in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        if 0 <= h+i < H and 0 <= w+j < W:
            if grid[h+i][w+j] == '.':
                if not memo[0][h+i][w+j] and not searched[h+i][w+j]:
                    memo[0][h+i][w+j] = True
                    d.appendleft((h+i, w+j, c))

    for i in range(-2, 3):
        for j in range(-2, 3):
            if 0 <= h+i < H and 0 <= w+j < W:
                if grid[h+i][w+j] == '.':
                    if not memo[0][h+i][w+j] and not memo[1][h+i][w+j] and not searched[h+i][w+j]:
                        memo[1][h+i][w+j] = True
                        d.append((h+i, w+j, c+1))

print(ans)

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

H, W = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())

grid = []
for i in range(H):
    grid.append(input().rstrip())

d = deque()
d.append((Ch-1, Cw-1, 0))

memo = [[[False] * W for _ in range(H)] for _ in range(1000)]
memo[0][Ch-1][Cw-1] = True

ans = -1

while d:
    h, w, c = d.popleft()

    if h == Dh-1 and w == Dw-1:
        ans = c
        break

    for i, j in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        if 0 <= h+i < H and 0 <= w+j < W:
            if grid[h+i][w+j] == '.':
                if not memo[c][h+i][w+j]:
                    memo[c][h+i][w+j] = True
                    d.appendleft((h+i, w+j, c))

    for i in range(-2, 3):
        for j in range(-2, 3):
            if 0 <= h+i < H and 0 <= w+j < W:
                if grid[h+i][w+j] == '.':
                    if not memo[c][h+i][w+j] and not memo[c+1][h+i][w+j]:
                        memo[c+1][h+i][w+j] = True
                        d.append((h+i, w+j, c+1))

print(ans)


Fixed submission:
from collections import deque

H, W = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())

grid = []
for i in range(H):
    grid.append(input().rstrip())

d = deque()
d.append((Ch-1, Cw-1, 0))

memo = [[[False] * W for _ in range(H)] for _ in range(2)]
memo[0][Ch-1][Cw-1] = True

searched = [[False] * W for _ in range(H)]

ans = -1

while d:
    h, w, c = d.popleft()

    if searched[h][w]:
        continue

    searched[h][w] = True

    if h == Dh-1 and w == Dw-1:
        ans = c
        break

    for i, j in [(0, 1), (0, -1), (1, 0), (-1, 0)]:
        if 0 <= h+i < H and 0 <= w+j < W:
            if grid[h+i][w+j] == '.':
                if not memo[0][h+i][w+j] and not searched[h+i][w+j]:
                    memo[0][h+i][w+j] = True
                    d.appendleft((h+i, w+j, c))

    for i in range(-2, 3):
        for j in range(-2, 3):
            if 0 <= h+i < H and 0 <= w+j < W:
                if grid[h+i][w+j] == '.':
                    if not memo[0][h+i][w+j] and not memo[1][h+i][w+j] and not searched[h+i][w+j]:
                        memo[1][h+i][w+j] = True
                        d.append((h+i, w+j, c+1))

print(ans)