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 = ['##' + input() + '##' for _ in range(h)]
for i in range(2):
    M.insert(0,'#'*(w+4))
    M.append('#'*(w+4))

INF = float('inf')
cost = [[INF for _ in range(w+4)] for _ in range(h+4)]
cost0 = deque()
ans = -1

cost0.append((ch+1, cw+1, 0))
cost[ch+1][cw+1] = 0

move = [(1,0),(0,1),(-1,0),(0,-1)]
warp = [(i,j) for i in range(-2,3) for j in range(-2,3) if (i,j) not in [(0,0)] + move]

cost1 = deque()

while cost0:
    h, w, c = cost0.popleft()
    cost1.append((h, w, c))
    
    for i,j in move:
        dh = h + i
        dw = w + j
        if M[dh][dw] == '.' and c < cost[dh][dw]: #コストが高いところから低いところに戻らないようにするため
            cost[dh][dw] = c
            cost0.appendleft((dh, dw, cost[dh][dw]))
    
    if len(cost0) == 0:
        while cost1:
            h, w, c = cost1.popleft()
            for i,j in warp:
                dh = h + i
                dw = w + j
                if M[dh][dw] == '.' and c+1 < cost[dh][dw]:  #無駄なワープをなくすため
                    cost[dh][dw] = c+1
                    cost0.append((dh, dw, cost[dh][dw]))
    if cost[Dh+1][Dw+1] != INF:
        ans = cost[Dh+1][Dw+1]

print(ans)

Fixed submission:
from collections import deque
def solve():  
    h, w = map(int,input().split())
    ch, cw = map(int,input().split())
    Dh, Dw = map(int,input().split())
    
    M = ['##' + input() + '##' for _ in range(h)]
    for i in range(2):
        M.insert(0,'#'*(w+4))
        M.append('#'*(w+4))
    
    INF = float('inf')
    cost = [[INF for _ in range(w+4)] for _ in range(h+4)]
    cost0 = deque()
    ans = -1
    
    cost0.append((ch+1, cw+1, 0))
    cost[ch+1][cw+1] = 0
    
    move = [(1,0),(0,1),(-1,0),(0,-1)]
    warp = [(i,j) for i in range(-2,3) for j in range(-2,3) if (i,j) not in [(0,0)] + move]
    
    cost1 = deque()
    
    while cost0:
        h, w, c = cost0.popleft()
        cost1.append((h, w, c))
        
        for i,j in move:
            dh = h + i
            dw = w + j
            if M[dh][dw] == '.' and c < cost[dh][dw]: #コストが高いところから低いところに戻らないようにするため
                cost[dh][dw] = c
                cost0.appendleft((dh, dw, cost[dh][dw]))
        
        if len(cost0) == 0:
            while cost1:
                h, w, c = cost1.popleft()
                for i,j in warp:
                    dh = h + i
                    dw = w + j
                    if M[dh][dw] == '.' and c+1 < cost[dh][dw]:  #無駄なワープをなくすため
                        cost[dh][dw] = c+1
                        cost0.append((dh, dw, cost[dh][dw]))
        if cost[Dh+1][Dw+1] != INF:
            ans = cost[Dh+1][Dw+1]
    
    print(ans)

if __name__ == "__main__":
    solve()

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 = ['##' + input() + '##' for _ in range(h)]
for i in range(2):
    M.insert(0,'#'*(w+4))
    M.append('#'*(w+4))

INF = float('inf')
cost = [[INF for _ in range(w+4)] for _ in range(h+4)]
cost0 = deque()
ans = -1

cost0.append((ch+1, cw+1, 0))
cost[ch+1][cw+1] = 0

move = [(1,0),(0,1),(-1,0),(0,-1)]
warp = [(i,j) for i in range(-2,3) for j in range(-2,3) if (i,j) not in [(0,0)] + move]

cost1 = deque()

while cost0:
    h, w, c = cost0.popleft()
    cost1.append((h, w, c))
    
    for i,j in move:
        dh = h + i
        dw = w + j
        if M[dh][dw] == '.' and c < cost[dh][dw]: #コストが高いところから低いところに戻らないようにするため
            cost[dh][dw] = c
            cost0.appendleft((dh, dw, cost[dh][dw]))
    
    if len(cost0) == 0:
        while cost1:
            h, w, c = cost1.popleft()
            for i,j in warp:
                dh = h + i
                dw = w + j
                if M[dh][dw] == '.' and c+1 < cost[dh][dw]:  #無駄なワープをなくすため
                    cost[dh][dw] = c+1
                    cost0.append((dh, dw, cost[dh][dw]))
    if cost[Dh+1][Dw+1] != INF:
        ans = cost[Dh+1][Dw+1]

print(ans)
                    
           

Fixed submission:
from collections import deque
def solve():  
    h, w = map(int,input().split())
    ch, cw = map(int,input().split())
    Dh, Dw = map(int,input().split())
    
    M = ['##' + input() + '##' for _ in range(h)]
    for i in range(2):
        M.insert(0,'#'*(w+4))
        M.append('#'*(w+4))
    
    INF = float('inf')
    cost = [[INF for _ in range(w+4)] for _ in range(h+4)]
    cost0 = deque()
    ans = -1
    
    cost0.append((ch+1, cw+1, 0))
    cost[ch+1][cw+1] = 0
    
    move = [(1,0),(0,1),(-1,0),(0,-1)]
    warp = [(i,j) for i in range(-2,3) for j in range(-2,3) if (i,j) not in [(0,0)] + move]
    
    cost1 = deque()
    
    while cost0:
        h, w, c = cost0.popleft()
        cost1.append((h, w, c))
        
        for i,j in move:
            dh = h + i
            dw = w + j
            if M[dh][dw] == '.' and c < cost[dh][dw]: #コストが高いところから低いところに戻らないようにするため
                cost[dh][dw] = c
                cost0.appendleft((dh, dw, cost[dh][dw]))
        
        if len(cost0) == 0:
            while cost1:
                h, w, c = cost1.popleft()
                for i,j in warp:
                    dh = h + i
                    dw = w + j
                    if M[dh][dw] == '.' and c+1 < cost[dh][dw]:  #無駄なワープをなくすため
                        cost[dh][dw] = c+1
                        cost0.append((dh, dw, cost[dh][dw]))
        if cost[Dh+1][Dw+1] != INF:
            ans = cost[Dh+1][Dw+1]
    
    print(ans)

if __name__ == "__main__":
    solve()

Buggy python submission (verdict: Runtime Error):
from collections import deque
h, w = map(int,input().split())
ch, cw = map(int,input().split())
dh, dw = map(int,input().split())

M = ['##' + input() + '##' for _ in range(h)]
for i in range(2):
    M.insert(0,'#'*(w+4))
    M.append('#'*(w+4))

INF = float('inf')
cost = [[INF for _ in range(w+4)] for _ in range(h+4)]
cost0 = deque()
ans = -1

cost0.append((ch+1, cw+1, 0))
cost[ch+1][cw+1] = 0

move = [(1,0),(0,1),(-1,0),(0,-1)]
warp = [(i,j) for i in range(-2,3) for j in range(-2,3) if (i,j) not in [(0,0)] + move]

cost1 = deque()

while cost0:
    h, w, c = cost0.popleft()
    cost1.append((h, w, c))
    
    for i,j in move:
        dh = h + i
        dw = w + j
        if M[dh][dw] == '.' and c < cost[dh][dw]: #コストが高いところから低いところに戻らないようにするため
            cost[dh][dw] = c
            cost0.appendleft((dh, dw, cost[dh][dw]))
    
    if len(cost0) == 0:
        while cost1:
            h, w, c = cost1.popleft()
            for i,j in warp:
                dh = h + i
                dw = w + j
                if S[dh][dw] == '.' and c+1 < cost[dh][dw]:  #無駄なワープをなくすため
                    cost[dh][dw] = c+1
                    cost0.append((dh, dw, cost[dh][dw]))
    if cost[dh+1][dw+1] != INF:
        ans = cost[dh+1][dw+1]

print(ans)

Fixed submission:
from collections import deque
def solve():  
    h, w = map(int,input().split())
    ch, cw = map(int,input().split())
    Dh, Dw = map(int,input().split())
    
    M = ['##' + input() + '##' for _ in range(h)]
    for i in range(2):
        M.insert(0,'#'*(w+4))
        M.append('#'*(w+4))
    
    INF = float('inf')
    cost = [[INF for _ in range(w+4)] for _ in range(h+4)]
    cost0 = deque()
    ans = -1
    
    cost0.append((ch+1, cw+1, 0))
    cost[ch+1][cw+1] = 0
    
    move = [(1,0),(0,1),(-1,0),(0,-1)]
    warp = [(i,j) for i in range(-2,3) for j in range(-2,3) if (i,j) not in [(0,0)] + move]
    
    cost1 = deque()
    
    while cost0:
        h, w, c = cost0.popleft()
        cost1.append((h, w, c))
        
        for i,j in move:
            dh = h + i
            dw = w + j
            if M[dh][dw] == '.' and c < cost[dh][dw]: #コストが高いところから低いところに戻らないようにするため
                cost[dh][dw] = c
                cost0.appendleft((dh, dw, cost[dh][dw]))
        
        if len(cost0) == 0:
            while cost1:
                h, w, c = cost1.popleft()
                for i,j in warp:
                    dh = h + i
                    dw = w + j
                    if M[dh][dw] == '.' and c+1 < cost[dh][dw]:  #無駄なワープをなくすため
                        cost[dh][dw] = c+1
                        cost0.append((dh, dw, cost[dh][dw]))
        if cost[Dh+1][Dw+1] != INF:
            ans = cost[Dh+1][Dw+1]
    
    print(ans)

if __name__ == "__main__":
    solve()