Buggy python submission (verdict: Time Limit Exceeded):
H,W = map(int,input().split())
Ch, Cw = map(lambda x: int(x)-1,input().split())
Dh, Dw = map(lambda x: int(x)-1,input().split())
S = []
for i in range(H):
  S.append(input())


from collections import deque

def bfs(sh,sw):
  queue = deque([(sh,sw)])
  d = [[None]*W for _ in range(H)]
  now = set()
  d[sh][sw]=0
  
  while queue:
    h,w = queue.popleft()
    now.add((h,w))
    for nh,nw in [(h-1,w),(h+1,w),(h,w-1),(h,w+1)]:
      if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
      queue.append((nh,nw))
      now.add((nh,nw))
      d[nh][nw]=d[h][w]
      if nh == Dh and nw == Dw:return d
    if queue: continue
    for h,w in now:
      for i in range(-2,3):
        for j in range(-2,3):
          if i==0 and abs(j)<=1: continue
          if j == 0 and abs(i)<=1: continue
          nh,nw = h-i,w-j
          if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
          d[nh][nw] = d[h][w]+1
          if nh == Dh and nw == Dw:return d
          queue.append((nh,nw))
    now = set()
    #print(queue)
  return d

d = bfs(Ch,Cw)
if d[Dh][Dw] == None: 
  print(-1)
  exit()
print(d[Dh][Dw])

Fixed submission:
H,W = map(int,input().split())
Ch, Cw = map(lambda x: int(x)-1,input().split())
Dh, Dw = map(lambda x: int(x)-1,input().split())
S = []
for i in range(H):
  S.append(input())


from collections import deque

def bfs(sh,sw):
  queue = deque([(sh,sw)])
  d = [[None]*W for _ in range(H)]
  now = set()
  d[sh][sw]=0
  
  while queue:
    h,w = queue.popleft()
    now.add((h,w))
    for nh,nw in [(h-1,w),(h+1,w),(h,w-1),(h,w+1)]:
      if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
      queue.append((nh,nw))
      now.add((nh,nw))
      d[nh][nw]=d[h][w]

    if queue: continue
    for h,w in now:
      for i in range(-2,3):
        for j in range(-2,3):
          if i==0 and abs(j)<=1: continue
          if j == 0 and abs(i)<=1: continue
          nh,nw = h-i,w-j
          if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
          d[nh][nw] = d[h][w]+1
          queue.append((nh,nw))
    now = set()
    #print(queue)
  return d

d = bfs(Ch,Cw)
if d[Dh][Dw] == None: 
  print(-1)
  exit()
print(d[Dh][Dw])

Buggy python submission (verdict: Time Limit Exceeded):
H,W = map(int,input().split())
Ch, Cw = map(lambda x: int(x)-1,input().split())
Dh, Dw = map(lambda x: int(x)-1,input().split())
S = []
for i in range(H):
  S.append(input())


from collections import deque

def bfs(sh,sw):
  queue = deque([(sh,sw)])
  d = {}
  now = set()
  d[(sh,sw)]=0
  
  while queue:
    h,w = queue.popleft()
    now.add((h,w))
    for nh,nw in [(h-1,w),(h+1,w),(h,w-1),(h,w+1)]:
      if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and (nh,nw) not in d) == False: continue
      queue.append((nh,nw))
      now.add((nh,nw))
      d[(nh,nw)]=d[(h,w)]

    if queue: continue
    for h,w in now:
      for i in range(-2,3):
        for j in range(-2,3):
          if i==0 and abs(j)<=1: continue
          if j == 0 and abs(i)<=1: continue
          nh,nw = h-i,w-j
          if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and (nh,nw) not in d) == False: continue
          d[(nh,nw)]=d[(h,w)]+1
          queue.append((nh,nw))
    now = set()
    #print(queue)
  return d

d = bfs(Ch,Cw)
if (Dh,Dw) not in d: 
  print(-1)
  exit()
print(d[(Dh,Dw)])

Fixed submission:
H,W = map(int,input().split())
Ch, Cw = map(lambda x: int(x)-1,input().split())
Dh, Dw = map(lambda x: int(x)-1,input().split())
S = []
for i in range(H):
  S.append(input())


from collections import deque

def bfs(sh,sw):
  queue = deque([(sh,sw)])
  d = [[None]*W for _ in range(H)]
  now = set()
  d[sh][sw]=0
  
  while queue:
    h,w = queue.popleft()
    now.add((h,w))
    for nh,nw in [(h-1,w),(h+1,w),(h,w-1),(h,w+1)]:
      if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
      queue.append((nh,nw))
      now.add((nh,nw))
      d[nh][nw]=d[h][w]

    if queue: continue
    for h,w in now:
      for i in range(-2,3):
        for j in range(-2,3):
          if i==0 and abs(j)<=1: continue
          if j == 0 and abs(i)<=1: continue
          nh,nw = h-i,w-j
          if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
          d[nh][nw] = d[h][w]+1
          queue.append((nh,nw))
    now = set()
    #print(queue)
  return d

d = bfs(Ch,Cw)
if d[Dh][Dw] == None: 
  print(-1)
  exit()
print(d[Dh][Dw])

Buggy python submission (verdict: Time Limit Exceeded):
H,W = map(int,input().split())
Ch, Cw = map(lambda x: int(x)-1,input().split())
Dh, Dw = map(lambda x: int(x)-1,input().split())
S = []
for i in range(H):
  S.append(input())


from collections import deque

def bfs(sh,sw):
  queue = deque([(sh,sw)])
  d = [[None]*W for _ in range(H)]
  now = set()
  d[sh][sw]=0
  
  while queue:
    h,w = queue.popleft()
    now.add((h,w))
    for nh,nw in [(h-1,w),(h+1,w),(h,w-1),(h,w+1)]:
      if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
      queue.append((nh,nw))
      now.add((nh,nw))
      d[nh][nw]=d[h][w]

    if queue: continue
    for h,w in now:
      for i in range(-2,3):
        for j in range(-2,3):
          if i==0 and abs(j)<=1: continue
          if j == 0 and abs(i)<=1: continue
          nh,nw = h-i,w-j
          if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
          d[nh][nw] = d[h][w]+1
          queue.append((nh,nw))
    now = set()
    #print(queue)
  return d

d = bfs(Ch,Cw)
if d[Dh][Dw] == None: 
  print(-1)
  exit()
print(d[Dh][Dw])

Fixed submission:
H,W = map(int,input().split())
Ch, Cw = map(lambda x: int(x)-1,input().split())
Dh, Dw = map(lambda x: int(x)-1,input().split())
S = []
for i in range(H):
  S.append(input())


from collections import deque

def bfs(sh,sw):
  queue = deque([(sh,sw)])
  d = [[None]*W for _ in range(H)]
  now = set()
  d[sh][sw]=0
  
  while queue:
    h,w = queue.popleft()
    now.add((h,w))
    for nh,nw in [(h-1,w),(h+1,w),(h,w-1),(h,w+1)]:
      if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
      queue.append((nh,nw))
      now.add((nh,nw))
      d[nh][nw]=d[h][w]

    if queue: continue
    for h,w in now:
      for i in range(-2,3):
        for j in range(-2,3):
          if i==0 and abs(j)<=1: continue
          if j == 0 and abs(i)<=1: continue
          nh,nw = h-i,w-j
          if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
          d[nh][nw] = d[h][w]+1
          queue.append((nh,nw))
    now = set()
    #print(queue)
  return d

d = bfs(Ch,Cw)
if d[Dh][Dw] == None: 
  print(-1)
  exit()
print(d[Dh][Dw])

Buggy python submission (verdict: Time Limit Exceeded):
H,W = map(int,input().split())
Ch, Cw = map(lambda x: int(x)-1,input().split())
Dh, Dw = map(lambda x: int(x)-1,input().split())
S = []
for i in range(H):
  S.append(input())


from collections import deque

def bfs(sh,sw):
  queue = deque([(sh,sw)])
  d = [[None]*W for _ in range(H)]
  now = deque()
  d[sh][sw]=0
  
  while queue:
    h,w = queue.popleft()
    now.append((h,w))
    for nh,nw in [(h-1,w),(h+1,w),(h,w-1),(h,w+1)]:
      if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
      queue.append((nh,nw))
      now.append((nh,nw))
      d[nh][nw]=d[h][w]

    if queue: continue
    while now:
      h,w = now.popleft()
      for i in range(-2,3):
        for j in range(-2,3):
          if i==0 and abs(j)<=1: continue
          if j == 0 and abs(i)<=1: continue
          nh,nw = h-i,w-j
          if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
          d[nh][nw] = d[h][w]+1
          queue.append((nh,nw))
    #print(queue)
  return d

d = bfs(Ch,Cw)
if d[Dh][Dw] == None: 
  print(-1)
  exit()
print(d[Dh][Dw])

Fixed submission:
H,W = map(int,input().split())
Ch, Cw = map(lambda x: int(x)-1,input().split())
Dh, Dw = map(lambda x: int(x)-1,input().split())
S = []
for i in range(H):
  S.append(input())


from collections import deque

def bfs(sh,sw):
  queue = deque([(sh,sw)])
  d = [[None]*W for _ in range(H)]
  now = set()
  d[sh][sw]=0
  
  while queue:
    h,w = queue.popleft()
    now.add((h,w))
    for nh,nw in [(h-1,w),(h+1,w),(h,w-1),(h,w+1)]:
      if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
      queue.append((nh,nw))
      now.add((nh,nw))
      d[nh][nw]=d[h][w]

    if queue: continue
    for h,w in now:
      for i in range(-2,3):
        for j in range(-2,3):
          if i==0 and abs(j)<=1: continue
          if j == 0 and abs(i)<=1: continue
          nh,nw = h-i,w-j
          if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
          d[nh][nw] = d[h][w]+1
          queue.append((nh,nw))
    now = set()
    #print(queue)
  return d

d = bfs(Ch,Cw)
if d[Dh][Dw] == None: 
  print(-1)
  exit()
print(d[Dh][Dw])

Buggy python submission (verdict: Time Limit Exceeded):
H,W = map(int,input().split())
Ch, Cw = map(lambda x: int(x)-1,input().split())
Dh, Dw = map(lambda x: int(x)-1,input().split())
S = []
for i in range(H):
  S.append(input())


from collections import deque

def bfs(sh,sw):
  queue = deque([(sh,sw)])
  d = [[None]*W for _ in range(H)]
  now = set()
  d[sh][sw]=0
  
  while queue:
    h,w = queue.popleft()
    now.add((h,w))
    for nh,nw in [(h-1,w),(h+1,w),(h,w-1),(h,w+1)]:
      if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
      queue.append((nh,nw))
      now.add((nh,nw))
      d[nh][nw]=d[h][w]

    if queue: continue
    for h,w in now:      
      for i in range(-2,3):
        for j in range(-2,3):
          if i==0 and abs(j)<=1: continue
          if j == 0 and abs(i)<=1: continue
          nh,nw = h-i,w-j
          if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
          d[nh][nw] = d[h][w]+1
          queue.append((nh,nw))
    #print(queue)
  return d

d = bfs(Ch,Cw)
if d[Dh][Dw] == None: 
  print(-1)
  exit()
print(d[Dh][Dw])

Fixed submission:
H,W = map(int,input().split())
Ch, Cw = map(lambda x: int(x)-1,input().split())
Dh, Dw = map(lambda x: int(x)-1,input().split())
S = []
for i in range(H):
  S.append(input())


from collections import deque

def bfs(sh,sw):
  queue = deque([(sh,sw)])
  d = [[None]*W for _ in range(H)]
  now = set()
  d[sh][sw]=0
  
  while queue:
    h,w = queue.popleft()
    now.add((h,w))
    for nh,nw in [(h-1,w),(h+1,w),(h,w-1),(h,w+1)]:
      if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
      queue.append((nh,nw))
      now.add((nh,nw))
      d[nh][nw]=d[h][w]

    if queue: continue
    for h,w in now:
      for i in range(-2,3):
        for j in range(-2,3):
          if i==0 and abs(j)<=1: continue
          if j == 0 and abs(i)<=1: continue
          nh,nw = h-i,w-j
          if (0<=nh<=H-1 and 0<=nw<=W-1 and S[nh][nw] == '.' and d[nh][nw] is None) == False: continue
          d[nh][nw] = d[h][w]+1
          queue.append((nh,nw))
    now = set()
    #print(queue)
  return d

d = bfs(Ch,Cw)
if d[Dh][Dw] == None: 
  print(-1)
  exit()
print(d[Dh][Dw])