### BUGGY CODE ###

# -*- coding: utf-8 -*-
from heapq import heapify, heappush, heappop
import numpy as np
import sys
from collections import deque
from collections import defaultdict
import heapq
import collections
import itertools
import bisect
from scipy.special import comb
import copy
import networkx as nx
sys.setrecursionlimit(10**6)

# lis_of_lis = [[] for _ in range(N)]


def zz():
    return list(map(int, sys.stdin.readline().split()))


def z():
    return int(sys.stdin.readline())


def S():
    return sys.stdin.readline()[:-1]


def C(line):
    return [sys.stdin.readline() for _ in range(line)]


H, W = zz()

c_h, c_w = zz()
d_h, d_w = zz()
board = []
c_h -= 1
c_w -= 1
d_h -= 1
d_w -= 1
for i in range(H):
    tmp = S()
    board.append(tmp)

que = deque([(c_h, c_w)])
INF = 1e9
dist = [[INF]*W for _ in range(H)]
dist[c_h][c_w] = 0
while que:
    # print(que)
    tmp = que.popleft()
    h, w = tmp
    d = dist[h][w]
    for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
        new_h = h + dy
        new_w = w + dx
        if new_h < 0 or H <= new_h or new_w < 0 or W <= new_w:
            continue
        if board[new_h][new_w] == '#':
            continue
        if dist[new_h][new_w] <= d:
            continue
        dist[new_h][new_w] = d
        que.appendleft((new_h, new_w))
    # 魔法
    for m_dy in range(-2, 3):
        for m_dx in range(-2, 3):
            new_h = h + m_dy
            new_w = w + m_dx
            if new_h < 0 or H <= new_h or new_w < 0 or W <= new_w:
                continue
            if board[new_h][new_w] == '#':
                continue
            if dist[new_h][new_w] <= d + 1:
                continue
            dist[new_h][new_w] = d + 1
            que.append((new_h, new_w))

ans = dist[d_h][d_w]
if ans == INF:
    print(-1)
else:
    print(ans)


### FIXED CODE ###

# -*- coding: utf-8 -*-
from heapq import heapify, heappush, heappop
import sys
from collections import deque
from collections import defaultdict
import heapq
import collections
import itertools
import bisect
import copy

sys.setrecursionlimit(10**6)

# lis_of_lis = [[] for _ in range(N)]


def zz():
    return list(map(int, sys.stdin.readline().split()))


def z():
    return int(sys.stdin.readline())


def S():
    return sys.stdin.readline()[:-1]


def C(line):
    return [sys.stdin.readline() for _ in range(line)]



def main(H, W, c_h, c_w, d_h, d_w):

    que = deque([(c_h, c_w)])
    INF = 1e9
    dist = [[INF]*W for _ in range(H)]
    dist[c_h][c_w] = 0
    while que:
        # print(que)
        tmp = que.popleft()
        h, w = tmp
        d = dist[h][w]
        for dy, dx in ((1, 0), (0, 1), (-1, 0), (0, -1)):
            new_h = h + dy
            new_w = w + dx
            if new_h < 0 or H <= new_h or new_w < 0 or W <= new_w:
                continue
            if board[new_h][new_w] == '#':
                continue
            if dist[new_h][new_w] <= d:
                continue
            dist[new_h][new_w] = d
            que.appendleft((new_h, new_w))
        # 魔法
        for m_dy in range(-2, 3):
            for m_dx in range(-2, 3):
                new_h = h + m_dy
                new_w = w + m_dx
                if new_h < 0 or H <= new_h or new_w < 0 or W <= new_w:
                    continue
                if board[new_h][new_w] == '#':
                    continue
                if dist[new_h][new_w] <= d + 1:
                    continue
                dist[new_h][new_w] = d + 1
                que.append((new_h, new_w))

    ans = dist[d_h][d_w]
    if ans == INF:
        print(-1)
    else:
        print(ans)


H, W = zz()
c_h, c_w = zz()
d_h, d_w = zz()
board = []
c_h -= 1
c_w -= 1
d_h -= 1
d_w -= 1
for i in range(H):
    tmp = S()
    board.append(tmp)
main(H, W, c_h, c_w, d_h, d_w)