Buggy python submission (verdict: Time Limit Exceeded):
import sys
from collections import deque
input = sys.stdin.readline


def main():
    h, w = map(int, input().split())
    ch, cw = map(int, input().split())
    dh, dw = map(int, input().split())
    
    ch += 1
    cw += 1
    dh += 1
    dw += 1
    
    
    s = ["#"*(w+4)]
    s.append("#"*(w+4))
    for i in range(h):
        s.append("##" + input()[:-1] + "##")
    s.append("#"*(w+4))
    s.append("#"*(w+4))
    
    
    ans = [[-1]*(w+4) for _ in range(h+4)]
    for i in range(h+4):
        for j in range(w+4):
            if s[i][j] == "#":
                ans[i][j] = -2
    ans[ch][cw] = 0
    
    move = [(-1, 0), (1, 0), (0, -1), (0, 1)]
    not_yet = deque([(ch, cw)])
    one_time = deque([])
    
    while len(not_yet) > 0:
        x, y = not_yet.popleft()
        one_time.append((x, y))
        for (p, q) in move:
            if ans[x+p][y+q] == -1:
                not_yet.append((x+p, y+q))
                ans[x+p][y+q] = ans[x][y]
                
        if len(not_yet) == 0:
            while len(one_time) > 0:
                x2, y2 = one_time.popleft()
                for i in range(x2-2, x2+3):
                    for j in range(y2-2, y2+3):
                        if ans[i][j] == -1:
                            ans[i][j] = ans[x2][y2]+1
                            not_yet.append((i, j))
          
    print(ans[dh][dw])
    
    
    
if __name__ == "__main__":
    main()


Fixed submission:
import sys
from collections import deque
input = sys.stdin.readline


def main():
    h, w = map(int, input().split())
    ch, cw = map(int, input().split())
    dh, dw = map(int, input().split())
    
    s = [input().replace("\n", "") for _ in range(h)]
    
    ans = [[-1]*w for _ in range(h)]
    ans[ch-1][cw-1] = 0
    not_yet = deque([(ch-1, cw-1)])
    one_time = deque([])
    while not_yet:
        x, y = not_yet.popleft()
        one_time.append((x, y))
        if x > 0 and ans[x-1][y] == -1 and s[x-1][y] == ".":
            not_yet.append((x-1, y))
            ans[x-1][y] = ans[x][y]
        if x < h-1 and ans[x+1][y] == -1 and s[x+1][y] == ".":
            not_yet.append((x+1, y))
            ans[x+1][y] = ans[x][y]
        if y > 0 and ans[x][y-1] == -1 and s[x][y-1] == ".":
            not_yet.append((x, y-1))
            ans[x][y-1] = ans[x][y]
        if y < w-1 and ans[x][y+1] == -1 and s[x][y+1] == ".":
            not_yet.append((x, y+1))
            ans[x][y+1] = ans[x][y]
        if not not_yet:
            while one_time:
                x2, y2 = one_time.popleft()
                for i in range(max(0, x2-2), min(h, x2+3)):
                    for j in range(max(0, y2-2), min(w, y2+3)):
                        if ans[i][j] == -1 and s[i][j] == ".":
                            ans[i][j] = ans[x][y]+1
                            not_yet.append((i, j))

    print(ans[dh-1][dw-1])
            
            
            
        
    
    
    
    
if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
from collections import deque
input = sys.stdin.readline


def main():
    h, w = map(int, input().split())
    ch, cw = map(int, input().split())
    dh, dw = map(int, input().split())
    
    ch += 1
    cw += 1
    dh += 1
    dw += 1
    
    
    s = ["#"*(w+4)]
    s.append("#"*(w+4))
    for i in range(h):
        s.append("##" + input().replace("\n", "") + "##")
    s.append("#"*(w+4))
    s.append("#"*(w+4))
    
    
    ans = [[-1]*(w+4) for _ in range(h+4)]
    for i in range(h+4):
        for j in range(w+4):
            if s[i][j] == "#":
                ans[i][j] = -2
    ans[ch][cw] = 0
    
    move = [(-1, 0), (1, 0), (0, -1), (0, 1)]
    not_yet = deque([(ch, cw)])
    one_time = deque([])
    
    while len(not_yet) > 0:
        x, y = not_yet.popleft()
        one_time.append((x, y))
        for (p, q) in move:
            if ans[x+p][y+q] == -1:
                not_yet.append((x+p, y+q))
                ans[x+p][y+q] = ans[x][y]
                
        if len(not_yet) == 0:
            while len(one_time) > 0:
                x2, y2 = one_time.popleft()
                for i in range(x2-2, x2+3):
                    for j in range(y2-2, y2+3):
                        if ans[i][j] == -1:
                            ans[i][j] = ans[x2][y2]+1
                            not_yet.append((i, j))
                            
                      
    print(ans[dh][dw])
    
    
    
if __name__ == "__main__":
    main()


Fixed submission:
import sys
from collections import deque
input = sys.stdin.readline


def main():
    h, w = map(int, input().split())
    ch, cw = map(int, input().split())
    dh, dw = map(int, input().split())
    
    s = [input().replace("\n", "") for _ in range(h)]
    
    ans = [[-1]*w for _ in range(h)]
    ans[ch-1][cw-1] = 0
    not_yet = deque([(ch-1, cw-1)])
    one_time = deque([])
    while not_yet:
        x, y = not_yet.popleft()
        one_time.append((x, y))
        if x > 0 and ans[x-1][y] == -1 and s[x-1][y] == ".":
            not_yet.append((x-1, y))
            ans[x-1][y] = ans[x][y]
        if x < h-1 and ans[x+1][y] == -1 and s[x+1][y] == ".":
            not_yet.append((x+1, y))
            ans[x+1][y] = ans[x][y]
        if y > 0 and ans[x][y-1] == -1 and s[x][y-1] == ".":
            not_yet.append((x, y-1))
            ans[x][y-1] = ans[x][y]
        if y < w-1 and ans[x][y+1] == -1 and s[x][y+1] == ".":
            not_yet.append((x, y+1))
            ans[x][y+1] = ans[x][y]
        if not not_yet:
            while one_time:
                x2, y2 = one_time.popleft()
                for i in range(max(0, x2-2), min(h, x2+3)):
                    for j in range(max(0, y2-2), min(w, y2+3)):
                        if ans[i][j] == -1 and s[i][j] == ".":
                            ans[i][j] = ans[x][y]+1
                            not_yet.append((i, j))

    print(ans[dh-1][dw-1])
            
            
            
        
    
    
    
    
if __name__ == "__main__":
    main()

Buggy python submission (verdict: Time Limit Exceeded):
import sys
from collections import deque
input = sys.stdin.readline


def main():
    h, w = map(int, input().split())
    ch, cw = map(int, input().split())
    dh, dw = map(int, input().split())
    
    ch += 1
    cw += 1
    dh += 1
    dw += 1
    
    
    s = ["#"*(w+4)]
    s.append("#"*(w+4))
    for i in range(h):
        s.append("##" + input().replace("\n", "") + "##")
    s.append("#"*(w+4))
    s.append("#"*(w+4))
    
    
    ans = [[-1]*(w+4) for _ in range(h+4)]
    for i in range(h+4):
        for j in range(w+4):
            if s[i][j] == "#":
                ans[i][j] = -2
    ans[ch][cw] = 0
    
    move = [(-1, 0), (1, 0), (0, -1), (0, 1)]
    not_yet = deque([(ch, cw)])
    one_time = deque([])
    
    while len(not_yet) > 0:
        x, y = not_yet.popleft()
        one_time.append((x, y))
        for (p, q) in move:
            if ans[x+p][y+q] == -1:
                not_yet.append((x+p, y+q))
                ans[x+p][y+q] = ans[x][y]
                
        if len(not_yet) == 0:
            while len(one_time) > 0:
                x2, y2 = one_time.popleft()
                for i in range(x2-2, x2+3):
                    for j in range(y2-2, y2+3):
                        if ans[i][j] == -1:
                            ans[i][j] = ans[x2][y2]+1
                            not_yet.append((i, j))
                            
                      
    print(ans[dh][dw])
    
    
    
if __name__ == "__main__":
    main()


Fixed submission:
import sys
from collections import deque
input = sys.stdin.readline


def main():
    h, w = map(int, input().split())
    ch, cw = map(int, input().split())
    dh, dw = map(int, input().split())
    
    s = [input().replace("\n", "") for _ in range(h)]
    
    ans = [[-1]*w for _ in range(h)]
    ans[ch-1][cw-1] = 0
    not_yet = deque([(ch-1, cw-1)])
    one_time = deque([])
    while not_yet:
        x, y = not_yet.popleft()
        one_time.append((x, y))
        if x > 0 and ans[x-1][y] == -1 and s[x-1][y] == ".":
            not_yet.append((x-1, y))
            ans[x-1][y] = ans[x][y]
        if x < h-1 and ans[x+1][y] == -1 and s[x+1][y] == ".":
            not_yet.append((x+1, y))
            ans[x+1][y] = ans[x][y]
        if y > 0 and ans[x][y-1] == -1 and s[x][y-1] == ".":
            not_yet.append((x, y-1))
            ans[x][y-1] = ans[x][y]
        if y < w-1 and ans[x][y+1] == -1 and s[x][y+1] == ".":
            not_yet.append((x, y+1))
            ans[x][y+1] = ans[x][y]
        if not not_yet:
            while one_time:
                x2, y2 = one_time.popleft()
                for i in range(max(0, x2-2), min(h, x2+3)):
                    for j in range(max(0, y2-2), min(w, y2+3)):
                        if ans[i][j] == -1 and s[i][j] == ".":
                            ans[i][j] = ans[x][y]+1
                            not_yet.append((i, j))

    print(ans[dh-1][dw-1])
            
            
            
        
    
    
    
    
if __name__ == "__main__":
    main()