Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*3000+sw
g = gh*3000+gw

S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [[float('inf')]*(W+4) for _ in range(H+4)]
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from heapq import heappush, heappop, heappushpop, heapify, heapreplace, merge
d = []
heapify(d)
heappush(d,s)
ans = float('inf')
while len(d)>0:
  a = heappop(d)
  cnt,a1 = divmod(a,10**7)
  h,w = divmod(a1,3000)
  if cnt>=ans:
    break
  visited[h][w] = cnt
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    if (h1,w1)==(gh,gw):
      ans = cnt
    if S[h1][w1]=='.':
      if visited[h1][w1]>cnt:
        visited[h1][w1]=cnt
        heappush(d,cnt*(10**7)+h1*3000+w1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    if (h2,w2)==(gh,gw):
      ans = cnt+1
    if S[h2][w2]=='.':
      if visited[h2][w2]>cnt+1:
        visited[h2][w2]=cnt+1
        heappush(d,(cnt+1)*(10**7)+h2*3000+w2)
ans = ans if ans<float('inf') else -1
print(ans)


Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1

S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [[float('inf')]*(W+4) for _ in range(H+4)]
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from heapq import heappush, heappop, heappushpop, heapify, heapreplace, merge
d = []
heapify(d)
heappush(d,(0,sh,sw))
ans = float('inf')
while len(d)>0:
  cnt,h,w = heappop(d)
  if cnt>=ans:
    break
  if visited[h][w]<=cnt:
    continue
  visited[h][w] = cnt
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[h1][w1]>cnt:
        heappush(d,(cnt,h1,w1))
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[h2][w2]>cnt+1:
        heappush(d,(cnt+1,h2,w2))
ans = ans if ans<float('inf') else -1
print(ans)


Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1

S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [[float('inf')]*(W+4) for _ in range(H+4)]
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from heapq import heappush, heappop, heappushpop, heapify, heapreplace, merge
d = []
heapify(d)
heappush(d,(0,sh,sw))
ans = float('inf')
while len(d)>0:
  cnt,h,w = heappop(d)
  if visited[h][w]<=cnt:
    continue
  if cnt>ans:
    break
  visited[h][w] = cnt
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[h1][w1]>cnt:
        heappush(d,(cnt,h1,w1))
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[h2][w2]>cnt+1:
        heappush(d,(cnt+1,h2,w2))
ans = ans if ans<float('inf') else -1
print(ans)


Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1

S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [[float('inf')]*(W+4) for _ in range(H+4)]
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from heapq import heappush, heappop, heappushpop, heapify, heapreplace, merge
d = []
heapify(d)
heappush(d,(0,sh,sw))

while len(d)>0:
  cnt,h,w = heappop(d)
  if visited[h][w]<=cnt:
    continue
  visited[h][w] = cnt
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    if S[h1][w1]=='.':
      if visited[h1][w1]>cnt:
        heappush(d,(cnt,h1,w1))
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    if S[h2][w2]=='.':
      if visited[h2][w2]>cnt+1:
        heappush(d,(cnt+1,h2,w2))
ans = visited[gh][gw] if visited[gh][gw]<float('inf') else -1
print(ans)


Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque
d = deque()
visited[g]=-1
d.append(g)

while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if S[h1][w1]=='.':
      visited[g]=-1
      d.append(a1)

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if visited[a1]==-1:
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.append(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if visited[a2]==-1:
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = ['*']*(W+4)
S[1] = ['*']*(W+4)
S[-2] = ['*']*(W+4)
S[-1] = ['*']*(W+4)
for h in range(2,H+2):
  S[h] = ['*']*2 + list(input()) + ['*']*2

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque
d = deque()
S[gh][gw] = 'g'
d.append(g)

while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if S[h1][w1]=='.':
      S[h1][w1]='g'
      d.append(a1)

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if S[h1][w1]=='g':
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.append(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if S[h2][w2]=='g':
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1

S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque
d = deque()
visited[sh*(W+4)+sw] = 0
d.append(sh*(W+4)+sw)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.append(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1

S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque
d = deque()
visited[sh*(W+4)+sw] = 0
d.append(sh*(W+4)+sw)

while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.append(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
ans = visited[gh*(W+4)+gw] if visited[gh*(W+4)+gw]<10**7 else -1
print(ans)

Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1

S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [[float('inf')]*(W+4) for _ in range(H+4)]
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque
d = deque()
visited[sh][sw] = 0
d.append(sh*(W+4)+sw)

while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[h][w]
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    if S[h1][w1]=='.':
      if visited[h1][w1]>cnt:
        visited[h1][w1]=cnt
        d.append((h1*(W+4)+w1))
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    if S[h2][w2]=='.':
      if visited[h2][w2]>cnt+1:
        visited[h2][w2]=cnt+1
        d.append((h2*(W+4)+w2))
ans = visited[gh][gw] if visited[gh][gw]<float('inf') else -1
print(ans)

Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1

S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [[float('inf')]*(W+4) for _ in range(H+4)]
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque
d = deque()
visited[sh][sw] = 0
d.append((sh,sw))

while len(d)>0:
  h,w = d.popleft()
  cnt = visited[h][w]
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    if S[h1][w1]=='.':
      if visited[h1][w1]>cnt:
        visited[h1][w1]=cnt
        d.append((h1,w1))
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    if S[h2][w2]=='.':
      if visited[h2][w2]>cnt+1:
        visited[h2][w2]=cnt+1
        d.append((h2,w2))
ans = visited[gh][gw] if visited[gh][gw]<float('inf') else -1
print(ans)

Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1

S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [[float('inf')]*(W+4) for _ in range(H+4)]
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque
d = deque()
visited[sh][sw] = 0
d.append((sh,sw,0))

while len(d)>0:
  h,w,cnt = d.popleft()
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    if S[h1][w1]=='.':
      if visited[h1][w1]>cnt:
        visited[h1][w1]=cnt
        d.append((h1,w1,cnt))
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    if S[h2][w2]=='.':
      if visited[h2][w2]>cnt+1:
        visited[h2][w2]=cnt+1
        d.append((h2,w2,cnt+1))
ans = visited[gh][gw] if visited[gh][gw]<float('inf') else -1
print(ans)

Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1

S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [[float('inf')]*(W+4) for _ in range(H+4)]
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque
d = deque()

d.append((sh,sw,0))

while len(d)>0:
  h,w,cnt = d.popleft()
  if visited[h][w]<=cnt:
    continue
  visited[h][w] = cnt
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    if S[h1][w1]=='.':
      if visited[h1][w1]>cnt:
        d.append((h1,w1,cnt))
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    if S[h2][w2]=='.':
      if visited[h2][w2]>cnt+1:
        d.append((h2,w2,cnt+1))
ans = visited[gh][gw] if visited[gh][gw]<float('inf') else -1
print(ans)

Fixed submission:
H, W = map(int, input().split())
sh, sw = map(int, input().split())
gh, gw = map(int, input().split())

sh += 1
sw += 1
gh += 1
gw += 1
s = sh*(W+4)+sw
g = gh*(W+4)+gw
S = [0]*(H+4)
S[0] = '*'*(W+4)
S[1] = '*'*(W+4)
S[-2] = '*'*(W+4)
S[-1] = '*'*(W+4)
for h in range(2,H+2):
  S[h] = '**' + input() + '**'

visited = [10**7]*((W+4)*(H+4))
dh1 = [0,1,0,-1]
dw1 = [1,0,-1,0]
dh2 = [2,2,2,2,2,1,1,1,1,0,0,-1,-1,-1,-1,-2,-2,-2,-2,-2]
dw2 = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]

from collections import deque

d = deque()
visited[s] = 0
d.append(s)
ans = 10**8
while len(d)>0:
  a = d.popleft()
  h,w = divmod(a,W+4)
  cnt = visited[a]
  if ans<=cnt:
    continue
  for i in range(4):
    h1 = h+dh1[i]
    w1 = w+dw1[i]
    a1 = h1*(W+4)+w1
    if (h1,w1)==(gh,gw):
      ans = min(ans,cnt)
    if S[h1][w1]=='.':
      if visited[a1]>cnt:
        visited[a1]=cnt
        d.appendleft(a1)
  for i in range(20):
    h2 = h+dh2[i]
    w2 = w+dw2[i]
    a2 = h2*(W+4)+w2
    if (h2,w2)==(gh,gw):
      ans = min(ans,cnt+1)
    if S[h2][w2]=='.':
      if visited[a2]>cnt+1:
        visited[a2]=cnt+1
        d.append(a2)
if ans==10**8:
  ans = -1
print(ans)