Buggy python submission (verdict: Time Limit Exceeded):
from _collections import deque
h,w=map(int,input().split())
cx,cy=map(int,input().split())
dx,dy=map(int,input().split())
s=[[] for _ in range(h+2)]
for i in range(h):
    x=list(input())
    x.insert(0,"#")
    x.append("#")
    s[i+1]=x
s[0]=s[-1]=["#"]*(w+2)




dep=[[10**10]*(w+2) for _ in range(h+2)]
dep[cx][cy]=0
data=deque([[cx,cy,0]])
while len(data)>0:
  xy=data.popleft()
  x,y=xy[0],xy[1]
  if xy[2]==dep[x][y]:
    if s[x-1][y]=="." and dep[x-1][y]>dep[x][y]:
        dep[x-1][y]=dep[x][y]
        data.append([x-1,y,dep[x][y]])
    if s[x+1][y] == "." and dep[x+1][y] > dep[x][y]:
        dep[x+1][y] = dep[x][y]
        data.append([x + 1,y,dep[x][y]])
    if s[x][y-1] == "." and dep[x][y-1] > dep[x][y]:
        dep[x][y-1] = dep[x][y]
        data.append([x,y-1,dep[x][y]])
    if s[x][y+1] == "." and dep[x][y+1] > dep[x][y]:
        dep[x][y+1] = dep[x][y]
        data.append([x,y+1,dep[x][y]])

    for i in range(5):
        for j in range(5):
            if 0<=x-2+i<=h+1 and 0<=y-2+j<=w+1 and s[x-2+i][y-2+j]=="." and dep[x-2+i][y-2+j]>dep[x][y]+1:
                dep[x-2+i][y-2+j]=dep[x][y]+1
                data.append([x-2+i,y-2+j,dep[x][y]+1])

print(dep[dx][dy] if dep[dx][dy]<10**10 else -1)



Fixed submission:
from _collections import deque


h,w=map(int,input().split())
cx,cy=map(int,input().split())
dx,dy=map(int,input().split())
s=[[] for _ in range(h+2)]
for i in range(h):
    x=list(input())
    x.insert(0,"#")
    x.append("#")
    s[i+1]=x
s[0]=s[-1]=["#"]*(w+2)




dep=[[10**10]*(w+2) for _ in range(h+2)]
dep[cx][cy]=0
data=deque([[cx,cy]])
while len(data)>0:
    xy=data.popleft()
    x,y=xy[0],xy[1]

    if s[x-1][y]=="." and dep[x-1][y]>dep[x][y]:
        dep[x-1][y]=dep[x][y]
        data.appendleft([x-1,y])
    if s[x+1][y] == "." and dep[x+1][y] > dep[x][y]:
        dep[x+1][y] = dep[x][y]
        data.appendleft([x + 1,y])
    if s[x][y-1] == "." and dep[x][y-1] > dep[x][y]:
        dep[x][y-1] = dep[x][y]
        data.appendleft([x,y-1])
    if s[x][y+1] == "." and dep[x][y+1] > dep[x][y]:
        dep[x][y+1] = dep[x][y]
        data.appendleft([x,y+1])

    for i in range(5):
        for j in range(5):
            if 0<=x-2+i<=h+1 and 0<=y-2+j<=w+1 and s[x-2+i][y-2+j]=="." and dep[x-2+i][y-2+j]>dep[x][y]+1:
                dep[x-2+i][y-2+j]=dep[x][y]+1
                data.append([x-2+i,y-2+j])

print(dep[dx][dy] if dep[dx][dy]<10**10 else -1)

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


h,w=map(int,input().split())
cx,cy=map(int,input().split())
dx,dy=map(int,input().split())
s=[[] for _ in range(h+2)]
for i in range(h):
    x=list(input())
    x.insert(0,"#")
    x.append("#")
    s[i+1]=x
s[0]=s[-1]=["#"]*(w+2)




dep=[[10**10]*(w+2) for _ in range(h+2)]
dep[cx][cy]=0
data=deque([[cx,cy]])
while len(data)>0:
    xy=data.popleft()
    x,y=xy[0],xy[1]

    if s[x-1][y]=="." and dep[x-1][y]>dep[x][y]:
        dep[x-1][y]=dep[x][y]
        data.appendleft([x-1,y])
    if s[x+1][y] == "." and dep[x+1][y] > dep[x][y]:
        dep[x+1][y] = dep[x][y]
        data.appendleft([x + 1,y])
    if s[x][y-1] == "." and dep[x][y-1] > dep[x][y]:
        dep[x][y-1] = dep[x][y]
        data.appendleft([x,y-1])
    if s[x][y+1] == "." and dep[x][y+1] > dep[x][y]:
        dep[x][y+1] = dep[x][y]
        data.appendleft([x,y+1])

    for i in range(5):
        for j in range(5):
            if 0<=x-2+i<=h+1 and 0<=y-2+j<=w+1 and s[x-2+i][y-2+j]=="." and dep[x-2+i][y-2+j]>dep[x][y]+1:
                dep[x-2+i][y-2+j]=dep[x][y]+1
                data.append([x-2+i,y-2+j])

print(dep[dx][dy] if dep[dx][dy]<10**10 else -1)





Fixed submission:
from _collections import deque


h,w=map(int,input().split())
cx,cy=map(int,input().split())
dx,dy=map(int,input().split())
s=[[] for _ in range(h+2)]
for i in range(h):
    x=list(input())
    x.insert(0,"#")
    x.append("#")
    s[i+1]=x
s[0]=s[-1]=["#"]*(w+2)




dep=[[10**10]*(w+2) for _ in range(h+2)]
dep[cx][cy]=0
data=deque([[cx,cy]])
while len(data)>0:
    xy=data.popleft()
    x,y=xy[0],xy[1]

    if s[x-1][y]=="." and dep[x-1][y]>dep[x][y]:
        dep[x-1][y]=dep[x][y]
        data.appendleft([x-1,y])
    if s[x+1][y] == "." and dep[x+1][y] > dep[x][y]:
        dep[x+1][y] = dep[x][y]
        data.appendleft([x + 1,y])
    if s[x][y-1] == "." and dep[x][y-1] > dep[x][y]:
        dep[x][y-1] = dep[x][y]
        data.appendleft([x,y-1])
    if s[x][y+1] == "." and dep[x][y+1] > dep[x][y]:
        dep[x][y+1] = dep[x][y]
        data.appendleft([x,y+1])

    for i in range(5):
        for j in range(5):
            if 0<=x-2+i<=h+1 and 0<=y-2+j<=w+1 and s[x-2+i][y-2+j]=="." and dep[x-2+i][y-2+j]>dep[x][y]+1:
                dep[x-2+i][y-2+j]=dep[x][y]+1
                data.append([x-2+i,y-2+j])

print(dep[dx][dy] if dep[dx][dy]<10**10 else -1)

Buggy python submission (verdict: Time Limit Exceeded):
from _collections import deque
h,w=map(int,input().split())
cx,cy=map(int,input().split())
dx,dy=map(int,input().split())
s=[[] for _ in range(h+2)]
for i in range(h):
    x=list(input())
    x.insert(0,"#")
    x.append("#")
    s[i+1]=x
s[0]=s[-1]=["#"]*(w+2)




dep=[[10**10]*(w+2) for _ in range(h+2)]
dep[cx][cy]=0
data=deque([[cx,cy]])
while len(data)>0:
    xy=data.popleft()
    x,y=xy[0],xy[1]

    if s[x-1][y]=="." and dep[x-1][y]>dep[x][y]:
        dep[x-1][y]=dep[x][y]
        data.append([x-1,y])
    if s[x+1][y] == "." and dep[x+1][y] > dep[x][y]:
        dep[x+1][y] = dep[x][y]
        data.append([x + 1,y])
    if s[x][y-1] == "." and dep[x][y-1] > dep[x][y]:
        dep[x][y-1] = dep[x][y]
        data.append([x,y-1])
    if s[x][y+1] == "." and dep[x][y+1] > dep[x][y]:
        dep[x][y+1] = dep[x][y]
        data.append([x,y+1])

    for i in range(5):
        for j in range(5):
            if 0<=x-2+i<=h+1 and 0<=y-2+j<=w+1 and s[x-2+i][y-2+j]=="." and dep[x-2+i][y-2+j]>dep[x][y]+1:
                dep[x-2+i][y-2+j]=dep[x][y]+1
                data.append([x-2+i,y-2+j])

print(dep[dx][dy] if dep[dx][dy]<10**10 else -1)



Fixed submission:
from _collections import deque


h,w=map(int,input().split())
cx,cy=map(int,input().split())
dx,dy=map(int,input().split())
s=[[] for _ in range(h+2)]
for i in range(h):
    x=list(input())
    x.insert(0,"#")
    x.append("#")
    s[i+1]=x
s[0]=s[-1]=["#"]*(w+2)




dep=[[10**10]*(w+2) for _ in range(h+2)]
dep[cx][cy]=0
data=deque([[cx,cy]])
while len(data)>0:
    xy=data.popleft()
    x,y=xy[0],xy[1]

    if s[x-1][y]=="." and dep[x-1][y]>dep[x][y]:
        dep[x-1][y]=dep[x][y]
        data.appendleft([x-1,y])
    if s[x+1][y] == "." and dep[x+1][y] > dep[x][y]:
        dep[x+1][y] = dep[x][y]
        data.appendleft([x + 1,y])
    if s[x][y-1] == "." and dep[x][y-1] > dep[x][y]:
        dep[x][y-1] = dep[x][y]
        data.appendleft([x,y-1])
    if s[x][y+1] == "." and dep[x][y+1] > dep[x][y]:
        dep[x][y+1] = dep[x][y]
        data.appendleft([x,y+1])

    for i in range(5):
        for j in range(5):
            if 0<=x-2+i<=h+1 and 0<=y-2+j<=w+1 and s[x-2+i][y-2+j]=="." and dep[x-2+i][y-2+j]>dep[x][y]+1:
                dep[x-2+i][y-2+j]=dep[x][y]+1
                data.append([x-2+i,y-2+j])

print(dep[dx][dy] if dep[dx][dy]<10**10 else -1)