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

H,W=map(int,input().split())
sh,sw=map(int,input().split())
gh,gw=map(int,input().split())
MAP=[input().strip() for i in range(H)]

ANS=[[1<<30]*W for i in range(H)]

sh-=1
sw-=1
gh-=1
gw-=1

ANS[sh][sw]=0

Q=[(0,sh,sw)]

while Q:
    sc,x,y=heapq.heappop(Q)

    if sc>ANS[x][y]:
        continue

    for i,j in [(x-2,y-2),(x-2,y-1),(x-2,y),(x-2,y+1),(x-2,y+2),(x-1,y-2),(x-1,y-1),(x-1,y),(x-1,y+1),(x-1,y+2),(x,y-2),(x,y-1),(x,y+1),(x,y+2),(x+1,y-2),(x+1,y-1),(x+1,y),(x+1,y+1),(x+1,y+2),(x+2,y-2),(x+2,y-1),(x+2,y),(x+2,y+1),(x+2,y+2)]:
        if 0<=i<H and 0<=j<W:
            if MAP[i][j]=="." and abs(i-x)+abs(j-y)==1 and ANS[i][j]>sc:
                ANS[i][j]=sc
                heapq.heappush(Q,(ANS[i][j],i,j))
            elif MAP[i][j]=="." and abs(i-x)+abs(j-y)>1 and ANS[i][j]>sc+1:
                ANS[i][j]=sc+1
                heapq.heappush(Q,(ANS[i][j],i,j))

if ANS[gh][gw]==1<<30:
    print(-1)
else:
    print(ANS[gh][gw])



Fixed submission:
import sys
input = sys.stdin.readline
import heapq

H,W=map(int,input().split())
sh,sw=map(int,input().split())
gh,gw=map(int,input().split())
MAP=[input().strip() for i in range(H)]

ANS=[[1<<30]*W for i in range(H)]

sh-=1
sw-=1
gh-=1
gw-=1

ANS[sh][sw]=0

def ca(sc,x,y):
    return sc*(10**8)+x*(10**4)+y

def inv(w):
    sc=w//(10**8)
    w%=(10**8)
    x=w//(10**4)
    y=w%(10**4)

    return sc,x,y

Q=[ca(0,sh,sw)]

while Q:
    sc,x,y=inv(heapq.heappop(Q))

    if sc>ANS[x][y]:
        continue

    for i,j in [(x-2,y-2),(x-2,y-1),(x-2,y),(x-2,y+1),(x-2,y+2),(x-1,y-2),(x-1,y-1),(x-1,y),(x-1,y+1),(x-1,y+2),(x,y-2),(x,y-1),(x,y+1),(x,y+2),(x+1,y-2),(x+1,y-1),(x+1,y),(x+1,y+1),(x+1,y+2),(x+2,y-2),(x+2,y-1),(x+2,y),(x+2,y+1),(x+2,y+2)]:
        if 0<=i<H and 0<=j<W:
            if MAP[i][j]=="." and abs(i-x)+abs(j-y)==1 and ANS[i][j]>sc:
                ANS[i][j]=sc
                heapq.heappush(Q,ca(ANS[i][j],i,j))
            elif MAP[i][j]=="." and abs(i-x)+abs(j-y)>1 and ANS[i][j]>sc+1:
                ANS[i][j]=sc+1
                heapq.heappush(Q,ca(ANS[i][j],i,j))

if ANS[gh][gw]==1<<30:
    print(-1)
else:
    print(ANS[gh][gw])

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

H,W=map(int,input().split())
sh,sw=map(int,input().split())
gh,gw=map(int,input().split())
MAP=[input().strip() for i in range(H)]

ANS=[[1<<30]*W for i in range(H)]

sh-=1
sw-=1
gh-=1
gw-=1

ANS[sh][sw]=0

Q=deque([(sh,sw,0)])

while Q:
    x,y,sc=Q.popleft()
    if ANS[x][y]<sc:
        continue

    for i,j in [(x-2,y-2),(x-2,y-1),(x-2,y),(x-2,y+1),(x-2,y+2),(x-1,y-2),(x-1,y-1),(x-1,y),(x-1,y+1),(x-1,y+2),(x,y-2),(x,y-1),(x,y+1),(x,y+2),(x+1,y-2),(x+1,y-1),(x+1,y),(x+1,y+1),(x+1,y+2),(x+2,y-2),(x+2,y-1),(x+2,y),(x+2,y+1),(x+2,y+2)]:
        if 0<=i<H and 0<=j<W:
            if MAP[i][j]=="." and abs(i-x)+abs(j-y)==1 and ANS[i][j]>ANS[x][y]:
                ANS[i][j]=ANS[x][y]
                Q.append((i,j,ANS[i][j]))
            elif MAP[i][j]=="." and abs(i-x)+abs(j-y)>1 and ANS[i][j]>ANS[x][y]+1:
                ANS[i][j]=ANS[x][y]+1
                Q.append((i,j,ANS[i][j]))

if ANS[gh][gw]==1<<30:
    print(-1)
else:
    print(ANS[gh][gw])



Fixed submission:
import sys
input = sys.stdin.readline
import heapq

H,W=map(int,input().split())
sh,sw=map(int,input().split())
gh,gw=map(int,input().split())
MAP=[input().strip() for i in range(H)]

ANS=[[1<<30]*W for i in range(H)]

sh-=1
sw-=1
gh-=1
gw-=1

ANS[sh][sw]=0

def ca(sc,x,y):
    return sc*(10**8)+x*(10**4)+y

def inv(w):
    sc=w//(10**8)
    w%=(10**8)
    x=w//(10**4)
    y=w%(10**4)

    return sc,x,y

Q=[ca(0,sh,sw)]

while Q:
    sc,x,y=inv(heapq.heappop(Q))

    if sc>ANS[x][y]:
        continue

    for i,j in [(x-2,y-2),(x-2,y-1),(x-2,y),(x-2,y+1),(x-2,y+2),(x-1,y-2),(x-1,y-1),(x-1,y),(x-1,y+1),(x-1,y+2),(x,y-2),(x,y-1),(x,y+1),(x,y+2),(x+1,y-2),(x+1,y-1),(x+1,y),(x+1,y+1),(x+1,y+2),(x+2,y-2),(x+2,y-1),(x+2,y),(x+2,y+1),(x+2,y+2)]:
        if 0<=i<H and 0<=j<W:
            if MAP[i][j]=="." and abs(i-x)+abs(j-y)==1 and ANS[i][j]>sc:
                ANS[i][j]=sc
                heapq.heappush(Q,ca(ANS[i][j],i,j))
            elif MAP[i][j]=="." and abs(i-x)+abs(j-y)>1 and ANS[i][j]>sc+1:
                ANS[i][j]=sc+1
                heapq.heappush(Q,ca(ANS[i][j],i,j))

if ANS[gh][gw]==1<<30:
    print(-1)
else:
    print(ANS[gh][gw])

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

H,W=map(int,input().split())
sh,sw=map(int,input().split())
gh,gw=map(int,input().split())
MAP=[input().strip() for i in range(H)]

ANS=[[1<<30]*W for i in range(H)]

sh-=1
sw-=1
gh-=1
gw-=1

ANS[sh][sw]=0

Q=deque([(sh,sw)])

while Q:
    x,y=Q.popleft()

    for i,j in [(x-2,y-2),(x-2,y-1),(x-2,y),(x-2,y+1),(x-2,y+2),(x-1,y-2),(x-1,y-1),(x-1,y),(x-1,y+1),(x-1,y+2),(x,y-2),(x,y-1),(x,y+1),(x,y+2),(x+1,y-2),(x+1,y-1),(x+1,y),(x+1,y+1),(x+1,y+2),(x+2,y-2),(x+2,y-1),(x+2,y),(x+2,y+1),(x+2,y+2)]:
        if 0<=i<H and 0<=j<W:
            if MAP[i][j]=="." and abs(i-x)+abs(j-y)==1 and ANS[i][j]>ANS[x][y]:
                ANS[i][j]=ANS[x][y]
                Q.append((i,j))
            elif MAP[i][j]=="." and abs(i-x)+abs(j-y)>1 and ANS[i][j]>ANS[x][y]+1:
                ANS[i][j]=ANS[x][y]+1
                Q.append((i,j))

if ANS[gh][gw]==1<<30:
    print(-1)
else:
    print(ANS[gh][gw])



Fixed submission:
import sys
input = sys.stdin.readline
import heapq

H,W=map(int,input().split())
sh,sw=map(int,input().split())
gh,gw=map(int,input().split())
MAP=[input().strip() for i in range(H)]

ANS=[[1<<30]*W for i in range(H)]

sh-=1
sw-=1
gh-=1
gw-=1

ANS[sh][sw]=0

def ca(sc,x,y):
    return sc*(10**8)+x*(10**4)+y

def inv(w):
    sc=w//(10**8)
    w%=(10**8)
    x=w//(10**4)
    y=w%(10**4)

    return sc,x,y

Q=[ca(0,sh,sw)]

while Q:
    sc,x,y=inv(heapq.heappop(Q))

    if sc>ANS[x][y]:
        continue

    for i,j in [(x-2,y-2),(x-2,y-1),(x-2,y),(x-2,y+1),(x-2,y+2),(x-1,y-2),(x-1,y-1),(x-1,y),(x-1,y+1),(x-1,y+2),(x,y-2),(x,y-1),(x,y+1),(x,y+2),(x+1,y-2),(x+1,y-1),(x+1,y),(x+1,y+1),(x+1,y+2),(x+2,y-2),(x+2,y-1),(x+2,y),(x+2,y+1),(x+2,y+2)]:
        if 0<=i<H and 0<=j<W:
            if MAP[i][j]=="." and abs(i-x)+abs(j-y)==1 and ANS[i][j]>sc:
                ANS[i][j]=sc
                heapq.heappush(Q,ca(ANS[i][j],i,j))
            elif MAP[i][j]=="." and abs(i-x)+abs(j-y)>1 and ANS[i][j]>sc+1:
                ANS[i][j]=sc+1
                heapq.heappush(Q,ca(ANS[i][j],i,j))

if ANS[gh][gw]==1<<30:
    print(-1)
else:
    print(ANS[gh][gw])

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

H,W=map(int,input().split())
sh,sw=map(int,input().split())
gh,gw=map(int,input().split())
MAP=[input().strip() for i in range(H)]

ANS=[[1<<30]*W for i in range(H)]

sh-=1
sw-=1
gh-=1
gw-=1

ANS[sh][sw]=0

Q=deque([(sh,sw)])

while Q:
    x,y=Q.popleft()

    for i in range(x-2,x+3):
        if 0<=i<H:           
            for j in range(y-2,y+3):
                if 0<=j<W:                
                    if MAP[i][j]=="." and abs(i-x)+abs(j-y)==1 and ANS[i][j]>ANS[x][y]:
                        ANS[i][j]=ANS[x][y]
                        Q.append((i,j))
                    elif MAP[i][j]=="." and abs(i-x)+abs(j-y)>1 and ANS[i][j]>ANS[x][y]+1:
                        ANS[i][j]=ANS[x][y]+1
                        Q.append((i,j))

if ANS[gh][gw]==1<<30:
    print(-1)
else:
    print(ANS[gh][gw])



Fixed submission:
import sys
input = sys.stdin.readline
import heapq

H,W=map(int,input().split())
sh,sw=map(int,input().split())
gh,gw=map(int,input().split())
MAP=[input().strip() for i in range(H)]

ANS=[[1<<30]*W for i in range(H)]

sh-=1
sw-=1
gh-=1
gw-=1

ANS[sh][sw]=0

def ca(sc,x,y):
    return sc*(10**8)+x*(10**4)+y

def inv(w):
    sc=w//(10**8)
    w%=(10**8)
    x=w//(10**4)
    y=w%(10**4)

    return sc,x,y

Q=[ca(0,sh,sw)]

while Q:
    sc,x,y=inv(heapq.heappop(Q))

    if sc>ANS[x][y]:
        continue

    for i,j in [(x-2,y-2),(x-2,y-1),(x-2,y),(x-2,y+1),(x-2,y+2),(x-1,y-2),(x-1,y-1),(x-1,y),(x-1,y+1),(x-1,y+2),(x,y-2),(x,y-1),(x,y+1),(x,y+2),(x+1,y-2),(x+1,y-1),(x+1,y),(x+1,y+1),(x+1,y+2),(x+2,y-2),(x+2,y-1),(x+2,y),(x+2,y+1),(x+2,y+2)]:
        if 0<=i<H and 0<=j<W:
            if MAP[i][j]=="." and abs(i-x)+abs(j-y)==1 and ANS[i][j]>sc:
                ANS[i][j]=sc
                heapq.heappush(Q,ca(ANS[i][j],i,j))
            elif MAP[i][j]=="." and abs(i-x)+abs(j-y)>1 and ANS[i][j]>sc+1:
                ANS[i][j]=sc+1
                heapq.heappush(Q,ca(ANS[i][j],i,j))

if ANS[gh][gw]==1<<30:
    print(-1)
else:
    print(ANS[gh][gw])