Buggy python submission (verdict: Time Limit Exceeded):
import sys

H, W = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())
S = [list(map(str, list(input()))) for i in range(H)]
floor = [[0] * W for i in range(H)]
floor[Ch - 1][Cw - 1] = 1


def water(x, y):
    if floor[y][x] != 0:

        # 上
        if y + 1 < H:
            if S[y + 1][x] != "#" and floor[y + 1][x] == 0:
                floor[y + 1][x] = floor[y][x]
                water(x, y + 1)
        # 下
        if y - 1 >= 0:
            if S[y - 1][x] != "#" and floor[y - 1][x] == 0:
                floor[y - 1][x] = floor[y][x]
                water(x, y - 1)
        # 右
        if x + 1 < W:
            if S[y][x + 1] != "#" and floor[y][x + 1] == 0:
                floor[y][x + 1] = floor[y][x]
                water(x + 1, y)
        # 左
        if x - 1 >= 0:
            if S[y][x - 1] != "#" and floor[y][x - 1] == 0:
                floor[y][x - 1] = floor[y][x]
                water(x - 1, y)


def warp(x, y, i):
    for Y in range(max(y - 2, 0), min(y + 2, H - 1) + 1):
        for X in range(max(x - 2, 0), min(x + 2, W - 1) + 1):
            if S[Y][X] != "#" and floor[Y][X] == 0:
                floor[Y][X] = i + 1
                water(X, Y)


# スタート地点に水を流す
water(Cw - 1, Ch - 1)
# print(floor)

# ワープ回数
for i in range(1, 1000):
    flag = False
    for y in range(H):
        for x in range(W):
            if floor[y][x] == i:
                warp(x, y, i)
                flag = True

    if floor[Dh - 1][Dw - 1] != 0:
        print(floor[Dh - 1][Dw - 1] - 1)
        # print(floor)
        sys.exit()

    if flag == False:
        print("-1")
        sys.exit()


Fixed submission:
import sys
from collections import deque

H, W = map(int, input().split())
Ch, Cw = map(int, input().split())
Dh, Dw = map(int, input().split())
S = [list(map(str, list(input()))) for i in range(H)]
floor = [[0] * W for i in range(H)]
floor[Ch - 1][Cw - 1] = 1



def water(x, y):
    if floor[y][x] != 0:
        kouho.append([x, y])
        # 上
        if y + 1 < H:
            if S[y + 1][x] != "#" and floor[y + 1][x] == 0:
                floor[y + 1][x] = floor[y][x]
                water(x, y + 1)
        # 下
        if y - 1 >= 0:
            if S[y - 1][x] != "#" and floor[y - 1][x] == 0:
                floor[y - 1][x] = floor[y][x]
                water(x, y - 1)
        # 右
        if x + 1 < W:
            if S[y][x + 1] != "#" and floor[y][x + 1] == 0:
                floor[y][x + 1] = floor[y][x]
                water(x + 1, y)
        # 左
        if x - 1 >= 0:
            if S[y][x - 1] != "#" and floor[y][x - 1] == 0:
                floor[y][x - 1] = floor[y][x]
                water(x - 1, y)


def warp(x, y, i):
    for Y in range(max(y - 2, 0), min(y + 2, H - 1) + 1):
        for X in range(max(x - 2, 0), min(x + 2, W - 1) + 1):
            if S[Y][X] != "#" and floor[Y][X] == 0:
                floor[Y][X] = i + 1
                water(X, Y)

kouho = deque()
# スタート地点に水を流す
water(Cw - 1, Ch - 1)
# print(floor)

# ワープ回数
for i in range(1, 1000000):
    flag = False
    new_kouho = kouho.copy()
    kouho.clear()
    for n in new_kouho:
        x = n[0]
        y = n[1]
        if floor[y][x] == i:
            warp(x, y, i)
            flag = True

    if floor[Dh - 1][Dw - 1] != 0:
        print(floor[Dh - 1][Dw - 1] - 1)
        # print(floor)
        sys.exit()

    if flag == False:
        print("-1")
        sys.exit()