Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H,W=map(int,input().split())
Ch,Cw=map(int,input().split())
Dh,Dw=map(int,input().split())
m=[list(input()) for _ in range(H)]
s=(Ch-1,Cw-1)
g=(Dh-1,Dw-1)
q=deque()
q.append(s)
d={s:0}
while q:
    y,x=q.popleft()
    flg=False
    for dy,dx in [(0,1),(1,0),(0,-1),(-1,0)]:
        ny=y+dy
        nx=x+dx
        if ny<0 or ny>=H or nx<0 or nx>=W:
            continue
        if m[ny][nx]=='.':
            if (ny,nx) not in d:
                q.append((ny,nx))
                d[(ny,nx)]=d[(y,x)]
            elif d[(ny,nx)]>d[(y,x)]:
                q.append((ny,nx))
                d[(ny,nx)]=d[(y,x)]
        else:
            flg=True
    if flg:
        for dy,dx in [(-2,-2),(-1,-2),(0,-2),(1,-2),(2,-2),(-2,-1),(-1,-1),(1,-1),(2,-1),(-2,0),(2,0),(-2,1),(-1,1),(1,1),(2,1),(-2,2),(-1,2),(0,2),(1,2),(2,2)]:
            ny=y+dy
            nx=x+dx
            if ny<0 or ny>=H or nx<0 or nx>=W:
                continue
            if m[ny][nx]=='.':
                if (ny,nx) not in d and (ny-1,nx) not in d and (ny,nx-1) not in d and (ny+1,nx) not in d and (ny+1,nx) not in d:
                    q.append((ny,nx))
                    d[(ny,nx)]=d[(y,x)]+1
                elif (ny,nx) in d and d[(ny,nx)]>d[(y,x)]+1:
                    q.append((ny,nx))
                    d[(ny,nx)]=d[(y,x)]+1
if g in d:
    print(d[g])
else:
    print(-1)

Fixed submission:
from collections import deque
INF=10**10
H,W=map(int,input().split())
Ch,Cw=map(int,input().split())
Dh,Dw=map(int,input().split())
m=[list(input()) for _ in range(H)]
s=(Ch-1,Cw-1)
g=(Dh-1,Dw-1)
d=[[INF]*W for _ in range(H)]
d[s[0]][s[1]]=0
q=deque()
q.append(s)
while q:
    y,x=q.pop()
    for dy,dx in [(0,1),(1,0),(0,-1),(-1,0)]:
        ny=y+dy
        nx=x+dx
        if ny<0 or ny>=H or nx<0 or nx>=W:
            continue
        if m[ny][nx]=='.' and d[ny][nx]>d[y][x]:
            q.append((ny,nx))
            d[ny][nx]=d[y][x]
    for dy in range(-2,3):
        for dx in range(-2,3):
            if abs(dy)+abs(dx)<=1:
                continue
            ny=y+dy
            nx=x+dx
            if ny<0 or ny>=H or nx<0 or nx>=W:
                continue
            if m[ny][nx]=='.' and d[ny][nx]>d[y][x]+1:
                q.appendleft((ny,nx))
                d[ny][nx]=d[y][x]+1
ans=d[g[0]][g[1]]
if ans<INF:
    print(ans)
else:
    print(-1)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H,W=map(int,input().split())
Ch,Cw=map(int,input().split())
Dh,Dw=map(int,input().split())
m=[list(input()) for _ in range(H)]
s=(Ch-1,Cw-1)
g=(Dh-1,Dw-1)
q=deque()
q.append(s)
d={s:0}
while q:
    y,x=q.popleft()
    for dy,dx in [(0,1),(1,0),(0,-1),(-1,0)]:
        ny=y+dy
        nx=x+dx
        if ny<0 or ny>=H or nx<0 or nx>=W:
            continue
        if m[ny][nx]=='.':
            if (ny,nx) not in d:
                q.append((ny,nx))
                d[(ny,nx)]=d[(y,x)]
            elif d[(ny,nx)]>d[(y,x)]:
                q.append((ny,nx))
                d[(ny,nx)]=d[(y,x)]
    for dy,dx in [(-2,-2),(-1,-2),(0,-2),(1,-2),(2,-2),(-2,-1),(-1,-1),(1,-1),(2,-1),(-2,0),(2,0),(-2,1),(-1,1),(1,1),(2,1),(-2,2),(-1,2),(0,2),(1,2),(2,2)]:
        ny=y+dy
        nx=x+dx
        if ny<0 or ny>=H or nx<0 or nx>=W:
            continue
        if m[ny][nx]=='.':
            if (ny,nx) not in d and (ny-1,nx) not in d and (ny,nx-1) not in d and (ny+1,nx) not in d and (ny+1,nx) not in d:
                q.append((ny,nx))
                d[(ny,nx)]=d[(y,x)]+1
            elif (ny,nx) in d and d[(ny,nx)]>d[(y,x)]+1:
                q.append((ny,nx))
                d[(ny,nx)]=d[(y,x)]+1
if g in d:
    print(d[g])
else:
    print(-1)

Fixed submission:
from collections import deque
INF=10**10
H,W=map(int,input().split())
Ch,Cw=map(int,input().split())
Dh,Dw=map(int,input().split())
m=[list(input()) for _ in range(H)]
s=(Ch-1,Cw-1)
g=(Dh-1,Dw-1)
d=[[INF]*W for _ in range(H)]
d[s[0]][s[1]]=0
q=deque()
q.append(s)
while q:
    y,x=q.pop()
    for dy,dx in [(0,1),(1,0),(0,-1),(-1,0)]:
        ny=y+dy
        nx=x+dx
        if ny<0 or ny>=H or nx<0 or nx>=W:
            continue
        if m[ny][nx]=='.' and d[ny][nx]>d[y][x]:
            q.append((ny,nx))
            d[ny][nx]=d[y][x]
    for dy in range(-2,3):
        for dx in range(-2,3):
            if abs(dy)+abs(dx)<=1:
                continue
            ny=y+dy
            nx=x+dx
            if ny<0 or ny>=H or nx<0 or nx>=W:
                continue
            if m[ny][nx]=='.' and d[ny][nx]>d[y][x]+1:
                q.appendleft((ny,nx))
                d[ny][nx]=d[y][x]+1
ans=d[g[0]][g[1]]
if ans<INF:
    print(ans)
else:
    print(-1)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
H,W=map(int,input().split())
Ch,Cw=map(int,input().split())
Dh,Dw=map(int,input().split())
m=[list(input()) for _ in range(H)]
s=(Ch-1,Cw-1)
g=(Dh-1,Dw-1)
q=deque()
q.append(s)
d={s:0}
while q:
    y,x=q.popleft()
    for dy,dx in [(0,1),(1,0),(0,-1),(-1,0)]:
        ny=y+dy
        nx=x+dx
        if ny<0 or ny>=H or nx<0 or nx>=W:
            continue
        if m[ny][nx]=='.':
            if (ny,nx) not in d:
                q.append((ny,nx))
                d[(ny,nx)]=d[(y,x)]
            elif d[(ny,nx)]>d[(y,x)]:
                q.append((ny,nx))
                d[(ny,nx)]=d[(y,x)]
    for dy,dx in [(-2,-2),(-1,-2),(0,-2),(1,-2),(2,-2),(-2,-1),(-1,-1),(1,-1),(2,-1),(-2,0),(2,0),(-2,1),(-1,1),(1,1),(2,1),(-2,2),(-1,2),(0,2),(1,2),(2,2)]:
        ny=y+dy
        nx=x+dx
        if ny<0 or ny>=H or nx<0 or nx>=W:
            continue
        if m[ny][nx]=='.':
            if (ny,nx) not in d:
                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
if g in d:
    print(d[g])
else:
    print(-1)

Fixed submission:
from collections import deque
INF=10**10
H,W=map(int,input().split())
Ch,Cw=map(int,input().split())
Dh,Dw=map(int,input().split())
m=[list(input()) for _ in range(H)]
s=(Ch-1,Cw-1)
g=(Dh-1,Dw-1)
d=[[INF]*W for _ in range(H)]
d[s[0]][s[1]]=0
q=deque()
q.append(s)
while q:
    y,x=q.pop()
    for dy,dx in [(0,1),(1,0),(0,-1),(-1,0)]:
        ny=y+dy
        nx=x+dx
        if ny<0 or ny>=H or nx<0 or nx>=W:
            continue
        if m[ny][nx]=='.' and d[ny][nx]>d[y][x]:
            q.append((ny,nx))
            d[ny][nx]=d[y][x]
    for dy in range(-2,3):
        for dx in range(-2,3):
            if abs(dy)+abs(dx)<=1:
                continue
            ny=y+dy
            nx=x+dx
            if ny<0 or ny>=H or nx<0 or nx>=W:
                continue
            if m[ny][nx]=='.' and d[ny][nx]>d[y][x]+1:
                q.appendleft((ny,nx))
                d[ny][nx]=d[y][x]+1
ans=d[g[0]][g[1]]
if ans<INF:
    print(ans)
else:
    print(-1)