Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
inf=float("inf")


def BFS():
    color=[["white" for _ in range(w)] for _ in range(h)]
    D=[[inf for _ in range(w)] for _ in range(h)]
    queue=deque([])

    x,y=C
    x -=1
    y -=1
    queue.append([x,y])
    D[x][y]=0

    for i in range(h):
        for j in range(w):
            if S[i][j]=="#":
                color[i][j]="black"

    while len(queue)>0:
        x,y=queue.popleft()
        for i,j in [[1,0],[0,1],[-1,0],[0,-1]]:
            X,Y=x+i,y+j
            if 0<=X<h and 0<=Y<w:
                if color[X][Y]!="black":
                    D[X][Y]=min(D[X][Y],D[x][y])
                    color[X][Y]="gray"
                    queue.appendleft([X,Y])

        for i in range(max(0,x-2),min(h,x+3)):
            for j in range(max(0,y-2),min(w,y+3)):
                X,Y=i,j
                if 0<=X<h and 0<=Y<w:
                    if color[X][Y]!="black":
                        D[X][Y]=min(D[X][Y],D[x][y]+1)
                        color[X][Y]="gray"
                        queue.append([X,Y])
        color[x][y]="black"

    return D[G[0]-1][G[1]-1]


h,w=map(int,input().split())
C=list(map(int,input().split()))
G=list(map(int,input().split()))
S=[list(input()) for _ in range(h)]

D=BFS()
print(D if D!=inf else -1)

Fixed submission:
from collections import deque
import sys
input=sys.stdin.readline
inf=float("inf")


def BFS():
    D=[[inf for _ in range(w)] for _ in range(h)]
    queue=deque()
    queue.append([Cx-1,Cy-1,0])
    D[Cx-1][Cy-1]=0

    while len(queue)>0:
        x,y,cnt=queue.popleft()
        for i,j in [[1,0],[0,1],[-1,0],[0,-1]]:
            X,Y=x+i,y+j
            if 0<=X<h and 0<=Y<w:
                if S[X][Y]=="." and D[X][Y]>cnt:
                    D[X][Y]=cnt
                    queue.appendleft([X,Y,cnt])

        for X in range(max(0,x-2),min(h,x+3)):
            for Y in range(max(0,y-2),min(w,y+3)):
                if S[X][Y]=="." and D[X][Y]>cnt+1:
                    D[X][Y]=cnt+1
                    queue.append([X,Y,cnt+1])

    return D[Dx-1][Dy-1]


h,w=map(int,input().split())
Cx,Cy=map(int,input().split())
Dx,Dy=map(int,input().split())
S=[list(input()) for _ in range(h)]

D=BFS()
print(D if D!=inf else -1)

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


def BFS():
    D=[[inf for _ in range(w)] for _ in range(h)]
    queue=deque()
    queue.append([Cx-1,Cy-1,0])
    D[Cx-1][Cy-1]=0

    while len(queue)>0:
        x,y,cnt=queue.popleft()
        for i,j in [[1,0],[0,1],[-1,0],[0,-1]]:
            X,Y=x+i,y+j
            if 0<=X<h and 0<=Y<w:
                if S[X][Y]=="." and D[X][Y]>cnt:
                    D[X][Y]=cnt
                    queue.append([X,Y,cnt])

        for X in range(max(0,x-2),min(h,x+3)):
            for Y in range(max(0,y-2),min(w,y+3)):
                if S[X][Y]=="." and D[X][Y]>cnt+1:
                    D[X][Y]=cnt+1
                    queue.append([X,Y,cnt+1])

    return D[Dx-1][Dy-1]


h,w=map(int,input().split())
Cx,Cy=map(int,input().split())
Dx,Dy=map(int,input().split())
S=[list(input()) for _ in range(h)]

D=BFS()
print(D if D!=inf else -1)

Fixed submission:
from collections import deque
import sys
input=sys.stdin.readline
inf=float("inf")


def BFS():
    D=[[inf for _ in range(w)] for _ in range(h)]
    queue=deque()
    queue.append([Cx-1,Cy-1,0])
    D[Cx-1][Cy-1]=0

    while len(queue)>0:
        x,y,cnt=queue.popleft()
        for i,j in [[1,0],[0,1],[-1,0],[0,-1]]:
            X,Y=x+i,y+j
            if 0<=X<h and 0<=Y<w:
                if S[X][Y]=="." and D[X][Y]>cnt:
                    D[X][Y]=cnt
                    queue.appendleft([X,Y,cnt])

        for X in range(max(0,x-2),min(h,x+3)):
            for Y in range(max(0,y-2),min(w,y+3)):
                if S[X][Y]=="." and D[X][Y]>cnt+1:
                    D[X][Y]=cnt+1
                    queue.append([X,Y,cnt+1])

    return D[Dx-1][Dy-1]


h,w=map(int,input().split())
Cx,Cy=map(int,input().split())
Dx,Dy=map(int,input().split())
S=[list(input()) for _ in range(h)]

D=BFS()
print(D if D!=inf else -1)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
inf=float("inf")


def BFS():
    D=[[inf for _ in range(w)] for _ in range(h)]
    queue=deque()
    queue.append([Cx-1,Cy-1,0])
    D[Cx-1][Cy-1]=0

    while len(queue)>0:
        x,y,cnt=queue.popleft()
        for i,j in [[1,0],[0,1],[-1,0],[0,-1]]:
            X,Y=x+i,y+j
            if 0<=X<h and 0<=Y<w:
                if S[X][Y]=="." and D[X][Y]>cnt:
                    D[X][Y]=cnt
                    queue.append([X,Y,cnt])

        for X in range(max(0,x-2),min(h,x+3)):
            for Y in range(max(0,y-2),min(w,y+3)):
                if S[X][Y]=="." and D[X][Y]>cnt+1:
                    D[X][Y]=cnt+1
                    queue.append([X,Y,cnt+1])

    return D[Dx-1][Dy-1]


h,w=map(int,input().split())
Cx,Cy=map(int,input().split())
Dx,Dy=map(int,input().split())
S=[list(input()) for _ in range(h)]

D=BFS()
print(D if D!=inf else -1)

Fixed submission:
from collections import deque
import sys
input=sys.stdin.readline
inf=float("inf")


def BFS():
    D=[[inf for _ in range(w)] for _ in range(h)]
    queue=deque()
    queue.append([Cx-1,Cy-1,0])
    D[Cx-1][Cy-1]=0

    while len(queue)>0:
        x,y,cnt=queue.popleft()
        for i,j in [[1,0],[0,1],[-1,0],[0,-1]]:
            X,Y=x+i,y+j
            if 0<=X<h and 0<=Y<w:
                if S[X][Y]=="." and D[X][Y]>cnt:
                    D[X][Y]=cnt
                    queue.appendleft([X,Y,cnt])

        for X in range(max(0,x-2),min(h,x+3)):
            for Y in range(max(0,y-2),min(w,y+3)):
                if S[X][Y]=="." and D[X][Y]>cnt+1:
                    D[X][Y]=cnt+1
                    queue.append([X,Y,cnt+1])

    return D[Dx-1][Dy-1]


h,w=map(int,input().split())
Cx,Cy=map(int,input().split())
Dx,Dy=map(int,input().split())
S=[list(input()) for _ in range(h)]

D=BFS()
print(D if D!=inf else -1)

Buggy python submission (verdict: Runtime Error):
from collections import deque
inf=float("inf")

import numpy as np
def BFS():
    color=[["white" for _ in range(w)] for _ in range(h)]
    D=[[inf for _ in range(w)] for _ in range(h)]
    queue=deque([])

    x,y=C
    x -=1
    y -=1
    queue.append([x,y])
    D[x][y]=0

    for i in range(h):
        for j in range(w):
            if S[i][j]=="#":
                color[i][j]="black"

    while len(queue)>0:
        x,y=queue.popleft()
        for X in range(max(0,x-3),min(h,x+3)):
            for Y in range(max(0,y-3),min(w,y+3)):
                if color[X][Y]!="black":
                    D[X][Y]=min(D[X][Y],D[x][y])
                    if color[X][Y]=="white":
                        queue.append([X,Y])
                    color[X][Y]="gray"
        color[x][y]="black"

    return D


def Check():
    point=0
    color=[["white" for _ in range(w)] for _ in range(h)]
    for i in range(h):
        for j in range(w):
            if D[i][j]==inf:
                color[i][j]="black"

    queue=deque([])
    for i in range(h):
        for j in range(w):
            if D[i][j]==0 and color[i][j]=="white":
                queue.append([i,j])
                while len(queue)>0:
                    x,y=queue.popleft()
                    for a,b in [[1,0],[0,1],[0,-1],[-1,0]]:
                        X,Y=x+a,y+b
                        if 0<=X<h and 0<=Y<w:
                            if color[X][Y]=="white":
                                color[X][Y]="gray"
                                queue.append([X,Y])
                    color[x][y]="black"
                point +=1

    return point


h,w=map(int,input().split())
C=list(map(int,input().split()))
G=list(map(int,input().split()))
S=[list(input()) for _ in range(h)]

D=BFS()
ans=True if D[G[0]-1][G[1]-1]!=inf else False
if ans==False:print(-1);exit()
print(Check()-1)

Fixed submission:
from collections import deque
import sys
input=sys.stdin.readline
inf=float("inf")


def BFS():
    D=[[inf for _ in range(w)] for _ in range(h)]
    queue=deque()
    queue.append([Cx-1,Cy-1,0])
    D[Cx-1][Cy-1]=0

    while len(queue)>0:
        x,y,cnt=queue.popleft()
        for i,j in [[1,0],[0,1],[-1,0],[0,-1]]:
            X,Y=x+i,y+j
            if 0<=X<h and 0<=Y<w:
                if S[X][Y]=="." and D[X][Y]>cnt:
                    D[X][Y]=cnt
                    queue.appendleft([X,Y,cnt])

        for X in range(max(0,x-2),min(h,x+3)):
            for Y in range(max(0,y-2),min(w,y+3)):
                if S[X][Y]=="." and D[X][Y]>cnt+1:
                    D[X][Y]=cnt+1
                    queue.append([X,Y,cnt+1])

    return D[Dx-1][Dy-1]


h,w=map(int,input().split())
Cx,Cy=map(int,input().split())
Dx,Dy=map(int,input().split())
S=[list(input()) for _ in range(h)]

D=BFS()
print(D if D!=inf else -1)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
inf=float("inf")


def BFS():
    color=[["white" for _ in range(w)] for _ in range(h)]
    D=[[inf for _ in range(w)] for _ in range(h)]
    queue=deque([])

    x,y=C
    x -=1
    y -=1
    queue.append([x,y])
    D[x][y]=0

    for i in range(h):
        for j in range(w):
            if S[i][j]=="#":
                color[i][j]="black"

    while len(queue)>0:
        x,y=queue.popleft()
        for i,j in [[1,0],[0,1],[-1,0],[0,-1]]:
            X,Y=x+i,y+j
            if 0<=X<h and 0<=Y<w:
                if color[X][Y]!="black":
                    D[X][Y]=min(D[X][Y],D[x][y])
                    color[X][Y]="gray"
                    queue.append([X,Y])

        for i in range(max(0,x-3),min(h,x+3)):
            for j in range(max(0,y-3),min(w,y+3)):
                X,Y=i,j
                if 0<=X<h and 0<=Y<w:
                    if color[X][Y]!="black":
                        D[X][Y]=min(D[X][Y],D[x][y]+1)
                        color[X][Y]="gray"
                        queue.append([X,Y])
        color[x][y]="black"

    return D[G[0]-1][G[1]-1]


h,w=map(int,input().split())
C=list(map(int,input().split()))
G=list(map(int,input().split()))
S=[list(input()) for _ in range(h)]

D=BFS()
print(D if D!=inf else -1)

Fixed submission:
from collections import deque
import sys
input=sys.stdin.readline
inf=float("inf")


def BFS():
    D=[[inf for _ in range(w)] for _ in range(h)]
    queue=deque()
    queue.append([Cx-1,Cy-1,0])
    D[Cx-1][Cy-1]=0

    while len(queue)>0:
        x,y,cnt=queue.popleft()
        for i,j in [[1,0],[0,1],[-1,0],[0,-1]]:
            X,Y=x+i,y+j
            if 0<=X<h and 0<=Y<w:
                if S[X][Y]=="." and D[X][Y]>cnt:
                    D[X][Y]=cnt
                    queue.appendleft([X,Y,cnt])

        for X in range(max(0,x-2),min(h,x+3)):
            for Y in range(max(0,y-2),min(w,y+3)):
                if S[X][Y]=="." and D[X][Y]>cnt+1:
                    D[X][Y]=cnt+1
                    queue.append([X,Y,cnt+1])

    return D[Dx-1][Dy-1]


h,w=map(int,input().split())
Cx,Cy=map(int,input().split())
Dx,Dy=map(int,input().split())
S=[list(input()) for _ in range(h)]

D=BFS()
print(D if D!=inf else -1)