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

res_S = [[-1]*W for i in range(H)]
dx = [1,-1,0,0]
ddx = [-2,-1,0,1,2,-2,-1,0,1,2,-2,-1,1,2,-2,-1,0,1,2,-2,-1,0,1,2]
dy = [0,0,1,-1]
ddy = [-2,-2,-2,-2,-2,-1,-1,-1,-1,-1,0,0,0,0,1,1,1,1,1,2,2,2,2,2]
count = 0

que = [(Ch,Cw)]
que_warp =[(Ch,Cw)]
res_S[Ch-1][Cw-1] = 0

while (que or que_warp):
    while (que):
        if count > 0:
            que_warp.append(que[0])
        for i in range(4):
            nx = int(que[0][0]+dx[i])
            ny = int(que[0][1]+dy[i])
            if (1<=nx<=H) and (1<=ny<=W):
                if res_S[nx-1][ny-1]<0 and S[nx-1][ny-1]=='.':
                    res_S[nx-1][ny-1]=count
                    que.append((nx,ny))
                    que_warp.append((nx,ny))
                    if (nx == Dh) and (ny == Dw):
                        print(res_S[Dh - 1][Dw - 1])
                        exit()
        que.pop(0)

    count += 1

    while(que_warp):
        for i in range(len(ddx)):
            nx = int(que_warp[0][0] + ddx[i])
            ny = int(que_warp[0][1] + ddy[i])
            if (1 <= nx <= H) and (1 <= ny <= W):
                if res_S[nx-1][ny-1]<0 and S[nx-1][ny-1]=='.':
                    res_S[nx-1][ny-1] = count
                    que.append((nx, ny))
                    if (nx == Dh) and (ny == Dw):
                        print(res_S[Dh - 1][Dw - 1])
                        exit()
        que_warp.pop(0)

print (res_S[Dh-1][Dw-1])

Fixed submission:
H,W = map(int,input().split())
Ch,Cw = map(int,input().split())
Dh,Dw = map(int,input().split())
S = [list(input()) for i in range(H)]
 
res_S = [[-1]*W for i in range(H)]
dx = [1,-1,0,0]
ddx = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]
dy = [0,0,1,-1]
ddy = [-2,-2,-2,-2,-2,-1,-1,-1,-1,0,0,1,1,1,1,2,2,2,2,2]
count = 0
 
que = [(Ch,Cw)]
que_warp =[(Ch,Cw)]
res_S[Ch-1][Cw-1] = 0
 
while (que or que_warp):
    l = len(que)
    while (que):
        if l > 0:
            que_warp.append(que[0])
            l -= 1
        for i in range(4):
            nx = int(que[0][0]+dx[i])
            ny = int(que[0][1]+dy[i])
            if (1<=nx<=H) and (1<=ny<=W):
                if res_S[nx-1][ny-1]<0 and S[nx-1][ny-1]=='.':
                    res_S[nx-1][ny-1]=count
                    que.append((nx,ny))
                    que_warp.append((nx,ny))
        que.pop(0)
 
    count += 1
 
    while(que_warp):
        for i in range(len(ddx)):
            nx = int(que_warp[0][0] + ddx[i])
            ny = int(que_warp[0][1] + ddy[i])
            if (1 <= nx <= H) and (1 <= ny <= W):
                if res_S[nx-1][ny-1]<0 and S[nx-1][ny-1]=='.':
                    res_S[nx-1][ny-1] = count
                    que.append((nx, ny))
        que_warp.pop(0)
 
print (res_S[Dh-1][Dw-1])

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

res_S = [[-1]*W for i in range(H)]
dx = [1,-1,0,0]
ddx = [-2,-1,0,1,2,-2,-1,0,1,2,-2,-1,1,2,-2,-1,0,1,2,-2,-1,0,1,2]
dy = [0,0,1,-1]
ddy = [-2,-2,-2,-2,-2,-1,-1,-1,-1,-1,0,0,0,0,1,1,1,1,1,2,2,2,2,2]
count = 0

que = [(Ch,Cw)]
que_warp =[(Ch,Cw)]
res_S[Ch-1][Cw-1] = 0

while (que or que_warp):
    while (que):
        if count > 0:
            que_warp.append(que[0])
        for i in range(4):
            nx = int(que[0][0]+dx[i])
            ny = int(que[0][1]+dy[i])
            if (1<=nx<=H) and (1<=ny<=W):
                if res_S[nx-1][ny-1]<0 and S[nx-1][ny-1]=='.':
                    res_S[nx-1][ny-1]=count
                    que.append((nx,ny))
                    que_warp.append((nx,ny))
        que.pop(0)

    count += 1

    while(que_warp):
        for i in range(len(ddx)):
            nx = int(que_warp[0][0] + ddx[i])
            ny = int(que_warp[0][1] + ddy[i])
            if (1 <= nx <= H) and (1 <= ny <= W):
                if res_S[nx-1][ny-1]<0 and S[nx-1][ny-1]=='.':
                    res_S[nx-1][ny-1] = count
                    que.append((nx, ny))
        que_warp.pop(0)

print (res_S[Dh-1][Dw-1])

Fixed submission:
H,W = map(int,input().split())
Ch,Cw = map(int,input().split())
Dh,Dw = map(int,input().split())
S = [list(input()) for i in range(H)]
 
res_S = [[-1]*W for i in range(H)]
dx = [1,-1,0,0]
ddx = [-2,-1,0,1,2,-2,-1,1,2,-2,2,-2,-1,1,2,-2,-1,0,1,2]
dy = [0,0,1,-1]
ddy = [-2,-2,-2,-2,-2,-1,-1,-1,-1,0,0,1,1,1,1,2,2,2,2,2]
count = 0
 
que = [(Ch,Cw)]
que_warp =[(Ch,Cw)]
res_S[Ch-1][Cw-1] = 0
 
while (que or que_warp):
    l = len(que)
    while (que):
        if l > 0:
            que_warp.append(que[0])
            l -= 1
        for i in range(4):
            nx = int(que[0][0]+dx[i])
            ny = int(que[0][1]+dy[i])
            if (1<=nx<=H) and (1<=ny<=W):
                if res_S[nx-1][ny-1]<0 and S[nx-1][ny-1]=='.':
                    res_S[nx-1][ny-1]=count
                    que.append((nx,ny))
                    que_warp.append((nx,ny))
        que.pop(0)
 
    count += 1
 
    while(que_warp):
        for i in range(len(ddx)):
            nx = int(que_warp[0][0] + ddx[i])
            ny = int(que_warp[0][1] + ddy[i])
            if (1 <= nx <= H) and (1 <= ny <= W):
                if res_S[nx-1][ny-1]<0 and S[nx-1][ny-1]=='.':
                    res_S[nx-1][ny-1] = count
                    que.append((nx, ny))
        que_warp.pop(0)
 
print (res_S[Dh-1][Dw-1])