Buggy python submission (verdict: Time Limit Exceeded):
def solve(h,w,ch,cw,dh,hw,s):
    d=[[1,0],[-1,0],[0,1],[0,-1]]
    warp = [(i, j) for i in range(-2, 3) for j in range(-2, 3) if (i, j) not in [(0, 0)] + d]
    INF=10**12
    path=[[INF]*w for _ in range(h)]
    ans=0
    st=[]
    st=deque()
    st.append((ch,cw,0))
    wp=[]
    wp=deque()
    while st:
      nx,ny,ncost=st.popleft()
      wp.append((nx,ny,ncost))
      path[nx][ny]=ncost
      for dx,dy in d:
        x=nx+dx
        y=ny+dy
        if (0<=x<=h-1) and (0<=y<=w-1):
          if s[x][y]!='#' and path[x][y]>ncost:
            path[x][y]=ncost
            st.append((x,y,ncost))
      if len(st)==0:
        while wp:
          nx,ny,ncost=wp.popleft()
          for dx,dy in warp:
              x,y=nx+dx,ny+dy
              if (0<=x<=h-1) and (0<=y<=w-1):
                if s[x][y]!='#' and path[x][y]>ncost+1:
                  path[x][y]=ncost+1
                  st.append((x,y,ncost+1))
    if path[dh][dw]==INF:
      print(-1)
    else:
      print(path[dh][dw])

if __name__ == '__main__':
    import sys
    input = sys.stdin.readline
    from collections import deque
    h,w=map(int,input().split())
    ch,cw=map(int,input().split())
    dh,dw=map(int,input().split())
    ch-=1
    cw-=1
    dh-=1
    dw-=1
    s=[input() for _ in range(h)]
    solve(h,w,ch,cw,dh,dw,s)

Fixed submission:
def solve(h,w,ch,cw,dh,hw,s):
    d=[[1,0],[-1,0],[0,1],[0,-1]]
    warp = [(i, j) for i in range(-2, 3) for j in range(-2, 3) if (i, j) not in [(0, 0)] + d]
    INF=10**12
    path=[[INF]*w for _ in range(h)]
    ans=0
    st=[]
    st=deque()
    st.append((ch,cw,0))
    wp=[]
    wp=deque()
    while st:
      nx,ny,ncost=st.popleft()
      wp.append((nx,ny,ncost))
      path[nx][ny]=ncost
      for dx,dy in d:
        x=nx+dx
        y=ny+dy
        if (0<=x<=h-1) and (0<=y<=w-1):
          if s[x][y]!='#' and path[x][y]>ncost:
            path[x][y]=ncost
            st.append((x,y,ncost))
      if len(st)==0:
        while wp:
          nx,ny,ncost=wp.popleft()
          for dx,dy in warp:
              x,y=nx+dx,ny+dy
              if (0<=x<=h-1) and (0<=y<=w-1):
                if s[x][y]!='#' and path[x][y]>ncost+1:
                  path[x][y]=ncost+1
                  st.append((x,y,ncost+1))
    if path[dh][dw]==INF:
      print(-1)
    else:
      print(path[dh][dw])

if __name__ == '__main__':
    import sys
    input = sys.stdin.readline
    from collections import deque
    h,w=map(int,input().split())
    ch,cw=map(int,input().split())
    dh,dw=map(int,input().split())
    ch-=1
    cw-=1
    dh-=1
    dw-=1
    s=[input() for _ in range(h)]
    solve(h,w,ch,cw,dh,dw,s)

Buggy python submission (verdict: Time Limit Exceeded):
def solve(h,w,ch,cw,dh,hw,s):
    d=[[1,0],[-1,0],[0,1],[0,-1]]
    INF=10**12
    path=[[INF]*w for _ in range(h)]
    ans=0
    st=[]
    st=deque()
    st.append((ch,cw,0))
    wp=[]
    wp=deque()
    while st:
      nx,ny,ncost=st.popleft()
      wp.append((nx,ny,ncost))
      path[nx][ny]=ncost
      for dx,dy in d:
        x=nx+dx
        y=ny+dy
        if (0<=x<=h-1) and (0<=y<=w-1):
          if s[x][y]!='#' and path[x][y]>ncost:
            path[x][y]=ncost
            st.append((x,y,ncost))
      if len(st)==0:
        while wp:
          nx,ny,ncost=wp.popleft()
          for i in range(-2,3):
            for j in range(-2,3):
              if (i,j)==(0,0) or (i,j)==(1,0) or (i,j)==(0,1) or (i,j)==(-1,0) or (i,j)==(0,-1):
                continue
              x,y=i+nx,j+ny
              if (0<=x<=h-1) and (0<=y<=w-1):
                if s[x][y]!='#' and path[x][y]>ncost+1:
                  path[x][y]=ncost+1
                  st.append((x,y,ncost+1))
    if path[dh][dw]==INF:
      print(-1)
    else:
      print(path[dh][dw])

if __name__ == '__main__':
    import sys
    input = sys.stdin.readline
    from collections import deque
    h,w=map(int,input().split())
    ch,cw=map(int,input().split())
    dh,dw=map(int,input().split())
    ch-=1
    cw-=1
    dh-=1
    dw-=1
    s=[input() for _ in range(h)]
    solve(h,w,ch,cw,dh,dw,s)

Fixed submission:
def solve(h,w,ch,cw,dh,hw,s):
    d=[[1,0],[-1,0],[0,1],[0,-1]]
    warp = [(i, j) for i in range(-2, 3) for j in range(-2, 3) if (i, j) not in [(0, 0)] + d]
    INF=10**12
    path=[[INF]*w for _ in range(h)]
    ans=0
    st=[]
    st=deque()
    st.append((ch,cw,0))
    wp=[]
    wp=deque()
    while st:
      nx,ny,ncost=st.popleft()
      wp.append((nx,ny,ncost))
      path[nx][ny]=ncost
      for dx,dy in d:
        x=nx+dx
        y=ny+dy
        if (0<=x<=h-1) and (0<=y<=w-1):
          if s[x][y]!='#' and path[x][y]>ncost:
            path[x][y]=ncost
            st.append((x,y,ncost))
      if len(st)==0:
        while wp:
          nx,ny,ncost=wp.popleft()
          for dx,dy in warp:
              x,y=nx+dx,ny+dy
              if (0<=x<=h-1) and (0<=y<=w-1):
                if s[x][y]!='#' and path[x][y]>ncost+1:
                  path[x][y]=ncost+1
                  st.append((x,y,ncost+1))
    if path[dh][dw]==INF:
      print(-1)
    else:
      print(path[dh][dw])

if __name__ == '__main__':
    import sys
    input = sys.stdin.readline
    from collections import deque
    h,w=map(int,input().split())
    ch,cw=map(int,input().split())
    dh,dw=map(int,input().split())
    ch-=1
    cw-=1
    dh-=1
    dw-=1
    s=[input() for _ in range(h)]
    solve(h,w,ch,cw,dh,dw,s)

Buggy python submission (verdict: Time Limit Exceeded):
def resolve():
    import sys
    input = sys.stdin.readline
    from collections import deque
    h,w=map(int,input().split())
    ch,cw=map(int,input().split())
    dh,dw=map(int,input().split())
    ch-=1
    cw-=1
    dh-=1
    dw-=1
    s=[input() for _ in range(h)]
    d=[[1,0],[-1,0],[0,1],[0,-1]]
    INF=10**12
    path=[[INF]*w for _ in range(h)]
    ans=0
    st=[]
    st=deque()
    st.append((ch,cw,0))
    wp=[]
    wp=deque()
    while st:
      nx,ny,ncost=st.popleft()
      wp.append((nx,ny,ncost))
      path[nx][ny]=ncost
      for dx,dy in d:
        x=nx+dx
        y=ny+dy
        if (0<=x<=h-1) and (0<=y<=w-1):
          if s[x][y]!='#' and path[x][y]>ncost:
            path[x][y]=ncost
            st.append((x,y,ncost))
      if len(st)==0:
        while wp:
          nx,ny,ncost=wp.popleft()
          for i in range(-2,3):
            for j in range(-2,3):
              if (i,j)==(0,0) or (i,j)==(1,0) or (i,j)==(0,1) or (i,j)==(-1,0) or (i,j)==(0,-1):
                continue
              x,y=i+nx,j+ny
              if (0<=x<=h-1) and (0<=y<=w-1):
                if s[x][y]!='#' and path[x][y]>ncost+1:
                  path[x][y]=ncost+1
                  st.append((x,y,ncost+1))
    if path[dh][dw]==INF:
      print(-1)
    else:
      print(path[dh][dw])

if __name__ == '__main__':
    resolve()

Fixed submission:
def solve(h,w,ch,cw,dh,hw,s):
    d=[[1,0],[-1,0],[0,1],[0,-1]]
    warp = [(i, j) for i in range(-2, 3) for j in range(-2, 3) if (i, j) not in [(0, 0)] + d]
    INF=10**12
    path=[[INF]*w for _ in range(h)]
    ans=0
    st=[]
    st=deque()
    st.append((ch,cw,0))
    wp=[]
    wp=deque()
    while st:
      nx,ny,ncost=st.popleft()
      wp.append((nx,ny,ncost))
      path[nx][ny]=ncost
      for dx,dy in d:
        x=nx+dx
        y=ny+dy
        if (0<=x<=h-1) and (0<=y<=w-1):
          if s[x][y]!='#' and path[x][y]>ncost:
            path[x][y]=ncost
            st.append((x,y,ncost))
      if len(st)==0:
        while wp:
          nx,ny,ncost=wp.popleft()
          for dx,dy in warp:
              x,y=nx+dx,ny+dy
              if (0<=x<=h-1) and (0<=y<=w-1):
                if s[x][y]!='#' and path[x][y]>ncost+1:
                  path[x][y]=ncost+1
                  st.append((x,y,ncost+1))
    if path[dh][dw]==INF:
      print(-1)
    else:
      print(path[dh][dw])

if __name__ == '__main__':
    import sys
    input = sys.stdin.readline
    from collections import deque
    h,w=map(int,input().split())
    ch,cw=map(int,input().split())
    dh,dw=map(int,input().split())
    ch-=1
    cw-=1
    dh-=1
    dw-=1
    s=[input() for _ in range(h)]
    solve(h,w,ch,cw,dh,dw,s)

Buggy python submission (verdict: Time Limit Exceeded):
def resolve():
    import sys
    input = sys.stdin.readline
    from collections import deque
    h,w=map(int,input().split())
    ch,cw=map(int,input().split())
    dh,dw=map(int,input().split())
    ch-=1
    cw-=1
    dh-=1
    dw-=1
    s=[input() for _ in range(h)]
    d=[[1,0],[-1,0],[0,1],[0,-1]]
    visit=[[False]*w for _ in range(h)]
    ans=0
    st=[]
    st=deque()
    st.append((ch,cw,0))
    while st:
      nx,ny,ncost=st.popleft()
      visit[nx][ny]=True
      if dh==nx and dw==ny:
        visit[dh][dw]=True
        ans=ncost
        break
      for dx,dy in d:
        x=nx+dx
        y=ny+dy
        if (0<=x<=h-1) and (0<=y<=w-1):
          if s[x][y]!='#' and visit[x][y]==False:
            st.appendleft((x,y,ncost))
      for i in range(-2,3):
        for j in range(-2,3):
          if (i,j)==(0,0) or (i,j)==(1,0) or (i,j)==(0,1) or (i,j)==(-1,0) or (i,j)==(0,-1):
            continue
          x,y=i+nx,j+ny
          if (0<=x<=h-1) and (0<=y<=w-1):
            if s[x][y]!='#' and visit[x][y]==False:
              st.append((x,y,ncost+1))
    if visit[dh][dw]==False:
      print(-1)
    else:
      print(ans)

if __name__ == '__main__':
    resolve()

Fixed submission:
def solve(h,w,ch,cw,dh,hw,s):
    d=[[1,0],[-1,0],[0,1],[0,-1]]
    warp = [(i, j) for i in range(-2, 3) for j in range(-2, 3) if (i, j) not in [(0, 0)] + d]
    INF=10**12
    path=[[INF]*w for _ in range(h)]
    ans=0
    st=[]
    st=deque()
    st.append((ch,cw,0))
    wp=[]
    wp=deque()
    while st:
      nx,ny,ncost=st.popleft()
      wp.append((nx,ny,ncost))
      path[nx][ny]=ncost
      for dx,dy in d:
        x=nx+dx
        y=ny+dy
        if (0<=x<=h-1) and (0<=y<=w-1):
          if s[x][y]!='#' and path[x][y]>ncost:
            path[x][y]=ncost
            st.append((x,y,ncost))
      if len(st)==0:
        while wp:
          nx,ny,ncost=wp.popleft()
          for dx,dy in warp:
              x,y=nx+dx,ny+dy
              if (0<=x<=h-1) and (0<=y<=w-1):
                if s[x][y]!='#' and path[x][y]>ncost+1:
                  path[x][y]=ncost+1
                  st.append((x,y,ncost+1))
    if path[dh][dw]==INF:
      print(-1)
    else:
      print(path[dh][dw])

if __name__ == '__main__':
    import sys
    input = sys.stdin.readline
    from collections import deque
    h,w=map(int,input().split())
    ch,cw=map(int,input().split())
    dh,dw=map(int,input().split())
    ch-=1
    cw-=1
    dh-=1
    dw-=1
    s=[input() for _ in range(h)]
    solve(h,w,ch,cw,dh,dw,s)

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())
ch-=1
cw-=1
dh-=1
dw-=1
s=[input() for _ in range(h)]
d=[[1,0],[-1,0],[0,1],[0,-1]]
visit=[[False]*w for _ in range(h)]
ans=0
st=[]
st=deque()
st.append((ch,cw,0))
while st:
  nx,ny,ncost=st.popleft()
  visit[nx][ny]=True
  if dh==nx and dw==ny:
    visit[dh][dw]=True
    ans=ncost
    break
  for dx,dy in d:
    x=nx+dx
    y=ny+dy
    if (0<=x<=h-1) and (0<=y<=w-1):
      if s[x][y]!='#' and visit[x][y]==False:
        st.appendleft((x,y,ncost))
  for i in range(-2,3):
    for j in range(-2,3):
      if (i,j)==(0,0) or (i,j)==(1,0) or (i,j)==(0,1) or (i,j)==(-1,0) or (i,j)==(0,-1):
        continue
      x,y=i+nx,j+ny
      if (0<=x<=h-1) and (0<=y<=w-1):
        if s[x][y]!='#' and visit[x][y]==False:
          st.append((x,y,ncost+1))
if visit[dh][dw]==False:
  print(-1)
else:
  print(ans)

Fixed submission:
def solve(h,w,ch,cw,dh,hw,s):
    d=[[1,0],[-1,0],[0,1],[0,-1]]
    warp = [(i, j) for i in range(-2, 3) for j in range(-2, 3) if (i, j) not in [(0, 0)] + d]
    INF=10**12
    path=[[INF]*w for _ in range(h)]
    ans=0
    st=[]
    st=deque()
    st.append((ch,cw,0))
    wp=[]
    wp=deque()
    while st:
      nx,ny,ncost=st.popleft()
      wp.append((nx,ny,ncost))
      path[nx][ny]=ncost
      for dx,dy in d:
        x=nx+dx
        y=ny+dy
        if (0<=x<=h-1) and (0<=y<=w-1):
          if s[x][y]!='#' and path[x][y]>ncost:
            path[x][y]=ncost
            st.append((x,y,ncost))
      if len(st)==0:
        while wp:
          nx,ny,ncost=wp.popleft()
          for dx,dy in warp:
              x,y=nx+dx,ny+dy
              if (0<=x<=h-1) and (0<=y<=w-1):
                if s[x][y]!='#' and path[x][y]>ncost+1:
                  path[x][y]=ncost+1
                  st.append((x,y,ncost+1))
    if path[dh][dw]==INF:
      print(-1)
    else:
      print(path[dh][dw])

if __name__ == '__main__':
    import sys
    input = sys.stdin.readline
    from collections import deque
    h,w=map(int,input().split())
    ch,cw=map(int,input().split())
    dh,dw=map(int,input().split())
    ch-=1
    cw-=1
    dh-=1
    dw-=1
    s=[input() for _ in range(h)]
    solve(h,w,ch,cw,dh,dw,s)