Buggy python submission (verdict: Time Limit Exceeded):
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
DD=[[-1]*W for i in range(H)]
dy=[-1,1,0,0]
dx=[0,0,1,-1,]
ey=[2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
ex=[0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    cnt=0
    for i in range(4):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
          q.appendleft((ny,nx))
          D[ny][nx]=D[y][x]
          DD[ny][nx]=1

    for i in range(20):
      my=y+ey[i]
      mx=x+ex[i]
      if 0<=my<H and 0<=mx<W:
        if A[my][mx]=='.' and D[my][mx]==10**8 and DD[my][mx]==-1:
          q.append((my,mx))
          D[my][mx]=D[y][x]+1
            
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])


Fixed submission:
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
DD=[[-1]*W for i in range(H)]
dy=[-1,1,0,0]
dx=[0,0,1,-1,]
ey=[2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
ex=[0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    cnt=0
    for i in range(4):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
          q.appendleft((ny,nx))
          D[ny][nx]=D[y][x]
          DD[ny][nx]=1

    for i in range(20):
      my=y+ey[i]
      mx=x+ex[i]
      if 0<=my<H and 0<=mx<W:
        if A[my][mx]=='.' and D[my][mx]==10**8 and DD[my][mx]==-1:
          q.append((my,mx))
          D[my][mx]=D[y][x]+1
            
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Buggy python submission (verdict: Runtime Error):
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
DD=[[-1]*W for i in range(H)]
dy=[-1,1,0,0]
dx=[0,0,1,-1,]
ey=[2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
ex=[0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    cnt=0
    for i in range(4):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
          q.appendleft((ny,nx))
          D[ny][nx]=D[y][x]
          DD[ny][nx]=1

    for i in range(20):
      my=y+ey[i]
      mx=x+ex[i]
      if 0<=my<H and 0<=mx<W:
        if A[my][mx]=='.' and D[my][mx]==10**8 and DD[my][my]==-1:
          q.append((my,mx))
          D[my][mx]=D[y][x]+1
            
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])


Fixed submission:
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
DD=[[-1]*W for i in range(H)]
dy=[-1,1,0,0]
dx=[0,0,1,-1,]
ey=[2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
ex=[0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    cnt=0
    for i in range(4):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
          q.appendleft((ny,nx))
          D[ny][nx]=D[y][x]
          DD[ny][nx]=1

    for i in range(20):
      my=y+ey[i]
      mx=x+ex[i]
      if 0<=my<H and 0<=mx<W:
        if A[my][mx]=='.' and D[my][mx]==10**8 and DD[my][mx]==-1:
          q.append((my,mx))
          D[my][mx]=D[y][x]+1
            
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Buggy python submission (verdict: Time Limit Exceeded):
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
dy=[-1,1,0,0]
dx=[0,0,1,-1,]
ey=[2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
ex=[0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    cnt=0
    for i in range(4):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
          q.appendleft((ny,nx))
          D[ny][nx]=D[y][x]

    for i in range(20):
      my=y+ey[i]
      mx=x+ex[i]
      if 0<=my<H and 0<=mx<W:
        if A[my][mx]=='.' and D[my][mx]==10**8:
          q.append((my,mx))
          D[my][mx]=D[y][x]+1
            
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Fixed submission:
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
DD=[[-1]*W for i in range(H)]
dy=[-1,1,0,0]
dx=[0,0,1,-1,]
ey=[2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
ex=[0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    cnt=0
    for i in range(4):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
          q.appendleft((ny,nx))
          D[ny][nx]=D[y][x]
          DD[ny][nx]=1

    for i in range(20):
      my=y+ey[i]
      mx=x+ex[i]
      if 0<=my<H and 0<=mx<W:
        if A[my][mx]=='.' and D[my][mx]==10**8 and DD[my][mx]==-1:
          q.append((my,mx))
          D[my][mx]=D[y][x]+1
            
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Buggy python submission (verdict: Time Limit Exceeded):
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
dy=[-1,1,0,0,2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dx=[0,0,1,-1,0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
from collections import deque
import sys
sys.setrecursionlimit(10**8) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  while len(q):
    y,x=q.popleft()
    for i in range(24):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if abs(ny-y)+abs(nx-x)==1:
          if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
            q.append((ny,nx))
            D[ny][nx]=D[y][x]
        else:
          if A[ny][nx]=='.':
            if D[ny][nx]==10**8:
              q.append((ny,nx))
              D[ny][nx]=D[y][x]+1
            elif D[ny][nx]>D[y][x]+1:
              q.append((ny,nx))
              D[ny][nx]=D[y][x]+1
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Fixed submission:
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
DD=[[-1]*W for i in range(H)]
dy=[-1,1,0,0]
dx=[0,0,1,-1,]
ey=[2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
ex=[0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    cnt=0
    for i in range(4):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
          q.appendleft((ny,nx))
          D[ny][nx]=D[y][x]
          DD[ny][nx]=1

    for i in range(20):
      my=y+ey[i]
      mx=x+ex[i]
      if 0<=my<H and 0<=mx<W:
        if A[my][mx]=='.' and D[my][mx]==10**8 and DD[my][mx]==-1:
          q.append((my,mx))
          D[my][mx]=D[y][x]+1
            
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Buggy python submission (verdict: Time Limit Exceeded):
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
dy=[-1,1,0,0,2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dx=[0,0,1,-1,0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  while len(q):
    y,x=q.popleft()
    for i in range(24):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if abs(ny-y)+abs(nx-x)==1:
          if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
            q.append((ny,nx))
            D[ny][nx]=D[y][x]
        else:
          if A[ny][nx]=='.':
            if D[ny][nx]==10**8:
              q.append((ny,nx))
              D[ny][nx]=D[y][x]+1
            elif D[ny][nx]>D[y][x]+1:
              q.append((ny,nx))
              D[ny][nx]=D[y][x]+1
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Fixed submission:
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
DD=[[-1]*W for i in range(H)]
dy=[-1,1,0,0]
dx=[0,0,1,-1,]
ey=[2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
ex=[0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    cnt=0
    for i in range(4):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
          q.appendleft((ny,nx))
          D[ny][nx]=D[y][x]
          DD[ny][nx]=1

    for i in range(20):
      my=y+ey[i]
      mx=x+ex[i]
      if 0<=my<H and 0<=mx<W:
        if A[my][mx]=='.' and D[my][mx]==10**8 and DD[my][mx]==-1:
          q.append((my,mx))
          D[my][mx]=D[y][x]+1
            
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Buggy python submission (verdict: Time Limit Exceeded):
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
dy=[-1,1,0,0,2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dx=[0,0,1,-1,0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    
    for i in range(24):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if abs(ny-y)+abs(nx-x)==1:
          if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
            q.append((ny,nx))
            D[ny][nx]=D[y][x]
        else:
          if A[ny][nx]=='.':
            if D[ny][nx]==10**8:
              q.append((ny,nx))
              D[ny][nx]=D[y][x]+1
            elif D[ny][nx]>D[y][x]+1:
              q.append((ny,nx))
              D[ny][nx]=D[y][x]+1
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Fixed submission:
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
DD=[[-1]*W for i in range(H)]
dy=[-1,1,0,0]
dx=[0,0,1,-1,]
ey=[2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
ex=[0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    cnt=0
    for i in range(4):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
          q.appendleft((ny,nx))
          D[ny][nx]=D[y][x]
          DD[ny][nx]=1

    for i in range(20):
      my=y+ey[i]
      mx=x+ex[i]
      if 0<=my<H and 0<=mx<W:
        if A[my][mx]=='.' and D[my][mx]==10**8 and DD[my][mx]==-1:
          q.append((my,mx))
          D[my][mx]=D[y][x]+1
            
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Buggy python submission (verdict: Time Limit Exceeded):
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
dy=[-1,1,0,0,2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dx=[0,0,1,-1,0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    
    for i in range(24):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if abs(ny-y)+abs(nx-x)==1:
          if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
            q.append((ny,nx))
            D[ny][nx]=D[y][x]
        else:
          if A[ny][nx]=='.':
            if D[ny][nx]==10**8:
              q.append((ny,nx))
              D[ny][nx]=D[y][x]+1
            elif D[ny][nx]>D[y][x]+1:
              q.append((ny,nx))
              D[ny][nx]=D[y][x]+1
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])

Fixed submission:
H,W=map(int, input().split())
Ch,Cw=map(int, input().split())
Dh,Dw=map(int, input().split())
A=[]
for i in range(H):
  d=list(input())
  A.append(d)
D=[[10**8]*W for i in range(H)]
DD=[[-1]*W for i in range(H)]
dy=[-1,1,0,0]
dx=[0,0,1,-1,]
ey=[2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
ex=[0,1,2,-1,-2,1,2,-1,-2,2,-2,1,2,-1,-2,0,1,2,-1,-2]
for h in range(H):
  for w in range(W):
    if A[h][w]=='#':
      D[h][w]=10**5
from collections import deque
import sys
sys.setrecursionlimit(10**7) 
def bfs(y,x):
  q=deque()
  q.append((y,x))
  
  while len(q):
    y,x=q.popleft()
    cnt=0
    for i in range(4):
      ny=y+dy[i]
      nx=x+dx[i]
      if 0<=ny<H and 0<=nx<W:
        if A[ny][nx]=='.' and D[y][x]<D[ny][nx]:
          q.appendleft((ny,nx))
          D[ny][nx]=D[y][x]
          DD[ny][nx]=1

    for i in range(20):
      my=y+ey[i]
      mx=x+ex[i]
      if 0<=my<H and 0<=mx<W:
        if A[my][mx]=='.' and D[my][mx]==10**8 and DD[my][mx]==-1:
          q.append((my,mx))
          D[my][mx]=D[y][x]+1
            
D[Ch-1][Cw-1]=0
bfs(Ch-1,Cw-1)
if D[Dh-1][Dw-1]==10**8:
  print(-1)
else:
  print(D[Dh-1][Dw-1])