Buggy python submission (verdict: Time Limit Exceeded):
#d
h,w = map(int, input().split())
ch,cw = map(int, input().split())
dh,dw = map(int, input().split())
s = [input() for _ in range(h)]
inf = 99999999
dist = [[inf]* w for i in range(h)]
queue = []
queue.append([ch-1,cw-1])
dist[ch-1][cw-1] = 0

dx=[1,0,-1,0]
dy=[0,1,0,-1]

wx=[-2,-2,-2,-2,-2,-1,-1,-1,-1,-1,0,0,0,0,1,1,1,1,1,2,2,2,2,2]
wy=[-2,-1,0,1,2,-2,-1,0,1,2,-2,-1,1,2,-2,-1,0,1,2,-2,-1,0,1,2]
import sys
warp = 0
wall = []
while True:
    while queue!=[]:
        y,x = map(int, queue.pop())

        if x == dw-1 and y ==dh-1:
            print(dist[y][x])
            sys.exit()

        for i in range(len(dx)):#まず壁探知
            next_x = x +dx[i]
            next_y = y +dy[i]

            if 0 <= next_x < len(s[0]) and 0 <= next_y < len(s):
                if dist[next_y][next_x] == inf: 
                    if s[next_y][next_x] == ".":
                        queue.append([next_y,next_x])
                        dist[next_y][next_x] = dist[y][x]
                    else:
                        wall.append([y,x]) 
    wall = list(map(list, set(map(tuple, wall))))
    while wall != []:
        y,x = map(int, wall.pop())
        for i in range(len(wx)):
            next_x = x +wx[i]
            next_y = y +wy[i]

            if 0 <= next_x < len(s[0]) and 0 <= next_y < len(s):
                if dist[next_y][next_x] == inf: 
                    if s[next_y][next_x] == ".":
                        queue.append([next_y,next_x])
                        dist[next_y][next_x] = dist[y][x]+1
    queue = list(map(list, set(map(tuple, queue))))
    
    if queue == []:
        print("-1")
        sys.exit()

Fixed submission:
#d
h,w = map(int, input().split())
ch,cw = map(int, input().split())
dh,dw = map(int, input().split())
s = [input() for _ in range(h)]
inf = 99999999
dist = [[inf]* w for i in range(h)]
queue = []
queue.append([ch-1,cw-1])
dist[ch-1][cw-1] = 0

dx=[1,0,-1,0]
dy=[0,1,0,-1]

wx=[-2,-2,-2,-2,-2,-1,-1,-1,-1,-1,0,0,0,0,1,1,1,1,1,2,2,2,2,2]
wy=[-2,-1,0,1,2,-2,-1,0,1,2,-2,-1,1,2,-2,-1,0,1,2,-2,-1,0,1,2]
import sys
warp = 0
wall = []
while True:
    while queue!=[]:
        y,x = map(int, queue.pop())

        if x == dw-1 and y ==dh-1:
            print(dist[y][x])
            sys.exit()

        for i in range(len(dx)):#まず壁探知
            next_x = x +dx[i]
            next_y = y +dy[i]

            if 0 <= next_x < len(s[0]) and 0 <= next_y < len(s):
                if dist[next_y][next_x] == inf: 
                    if s[next_y][next_x] == ".":
                        queue.append([next_y,next_x])
                        dist[next_y][next_x] = dist[y][x]
                    else:
                        wall.append([y,x]) 
    wall = list(map(list, set(map(tuple, wall))))
    while wall != []:
        y,x = map(int, wall.pop())
        for i in range(len(wx)):
            next_x = x +wx[i]
            next_y = y +wy[i]

            if 0 <= next_x < len(s[0]) and 0 <= next_y < len(s):
                if dist[next_y][next_x] == inf: 
                    if s[next_y][next_x] == ".":
                        queue.append([next_y,next_x])
                        dist[next_y][next_x] = dist[y][x]+1
    queue = list(map(list, set(map(tuple, queue))))
    
    if queue == []:
        print("-1")
        sys.exit()

Buggy python submission (verdict: Time Limit Exceeded):
#d
h,w = map(int, input().split())
ch,cw = map(int, input().split())
dh,dw = map(int, input().split())
s = [input() for _ in range(h)]
inf = 99999999
dist = [[inf]* w for i in range(h)]
queue = []
queue.append([ch-1,cw-1])
dist[ch-1][cw-1] = 0

dx=[1,0,-1,0]
dy=[0,1,0,-1]

wx=[-2,-2,-2,-2,-2,-1,-1,-1,-1,-1,0,0,0,0,1,1,1,1,1,2,2,2,2,2]
wy=[-2,-1,0,1,2,-2,-1,0,1,2,-2,-1,1,2,-2,-1,0,1,2,-2,-1,0,1,2]
import sys
warp = 0
wall = []
while True:
    while queue!=[]:
        y,x = map(int, queue.pop())

        if x == dw-1 and y ==dh-1:
            print(dist[y][x])
            sys.exit()

        for i in range(len(dx)):#まず壁探知
            next_x = x +dx[i]
            next_y = y +dy[i]

            if 0 <= next_x < len(s[0]) and 0 <= next_y < len(s):
                if dist[next_y][next_x] == inf: 
                    if s[next_y][next_x] == ".":
                        queue.append([next_y,next_x])
                        dist[next_y][next_x] = dist[y][x]
                    else:
                        wall.append([y,x]) 
    while wall != []:
        y,x = map(int, wall.pop())
        for i in range(len(wx)):
            next_x = x +wx[i]
            next_y = y +wy[i]

            if 0 <= next_x < len(s[0]) and 0 <= next_y < len(s):
                if dist[next_y][next_x] == inf: 
                    if s[next_y][next_x] == ".":
                        queue.append([next_y,next_x])
                        dist[next_y][next_x] = dist[y][x]+1


Fixed submission:
#d
h,w = map(int, input().split())
ch,cw = map(int, input().split())
dh,dw = map(int, input().split())
s = [input() for _ in range(h)]
inf = 99999999
dist = [[inf]* w for i in range(h)]
queue = []
queue.append([ch-1,cw-1])
dist[ch-1][cw-1] = 0

dx=[1,0,-1,0]
dy=[0,1,0,-1]

wx=[-2,-2,-2,-2,-2,-1,-1,-1,-1,-1,0,0,0,0,1,1,1,1,1,2,2,2,2,2]
wy=[-2,-1,0,1,2,-2,-1,0,1,2,-2,-1,1,2,-2,-1,0,1,2,-2,-1,0,1,2]
import sys
warp = 0
wall = []
while True:
    while queue!=[]:
        y,x = map(int, queue.pop())

        if x == dw-1 and y ==dh-1:
            print(dist[y][x])
            sys.exit()

        for i in range(len(dx)):#まず壁探知
            next_x = x +dx[i]
            next_y = y +dy[i]

            if 0 <= next_x < len(s[0]) and 0 <= next_y < len(s):
                if dist[next_y][next_x] == inf: 
                    if s[next_y][next_x] == ".":
                        queue.append([next_y,next_x])
                        dist[next_y][next_x] = dist[y][x]
                    else:
                        wall.append([y,x]) 
    wall = list(map(list, set(map(tuple, wall))))
    while wall != []:
        y,x = map(int, wall.pop())
        for i in range(len(wx)):
            next_x = x +wx[i]
            next_y = y +wy[i]

            if 0 <= next_x < len(s[0]) and 0 <= next_y < len(s):
                if dist[next_y][next_x] == inf: 
                    if s[next_y][next_x] == ".":
                        queue.append([next_y,next_x])
                        dist[next_y][next_x] = dist[y][x]+1
    queue = list(map(list, set(map(tuple, queue))))
    
    if queue == []:
        print("-1")
        sys.exit()