### BUGGY 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 dijkstra(path, N, start):
    visited = [False] * N
    que = [(0, start)]
    heapify(que)  # 始点aから各頂点への(距離, 頂点ID)
    dist = [-1] * N  # 始点aから各頂点への距離
    dist[start] = 0  # 始点aからaへの距離は0
    while que:
        d, v = heappop(que)  # 始点から最短距離の頂点を(確定ノード)を取り出す
        visited[v] = True  # 確定フラグを立てる
        # 接続先ノードの情報を更新する
        for d, to in path[v]:
            cost = dist[v] + d
            if dist[to] < 0 or cost < dist[to]:
                dist[to] = cost
                if not visited[to]:
                    heappush(que, (cost, to))
    return dist


# MAGIC = ((-2, -2), (-1, -2), (0, -2), (1, -2), (2, -2),
#          (-2, -1), (-1, -1), (0, -1), (1, -1), (2, -1),
#          (-2, 0), (-1, 0), (0, 0), (1, 0), (2, 0),
#          (-2, 1), (-1, 1), (0, 1), (1, 1), (2, 1),
#          (-2, -2), (-1, 2), (0, 2), (1, 2), (2, 2))

MAGIC = ((-2, -2), (-1, -2), (1, -2), (2, -2),
         (-2, -1), (-1, -1),  (1, -1), (2, -1),
         (-2, 1), (-1, 1), (1, 1), (2, 1),
         (-2, -2), (-1, 2), (1, 2), (2, 2))
H, W = zz()
c_h, c_w = zz()
d_h, d_w = zz()
board = []
N = H*W
for i in range(H):
    tmp = S()
    # N += tmp.count('.')
    board.append(tmp)

path = [[] for _ in range(N)]
for h in range(H):
    for w in range(W):
        if board[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] == '.'):
                    path[h*W + w].append((0, new_h*W + new_w))
                    path[new_h*W + new_w].append((0, h*W + w))
                else:
                    #  隣は壁
                    new_h = h + dy*2
                    new_w = w + dx*2
                    if new_h < 0 or H <= new_h or new_w < 0 or W <= new_w:
                        continue
                    if(board[new_h][new_w] == '.'):  # 2個先は存在
                        path[h*W + w].append((1, new_h*W + new_w))
                        path[new_h*W + new_w].append((1, h*W + w))
                for dy, dx in MAGIC:
                    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] == '.'):
                        path[h*W + w].append((1, new_h*W + new_w))
                        path[new_h*W + new_w].append((1, h*W + w))

c_h -= 1
c_w -= 1
d_h -= 1
d_w -= 1
dist = dijkstra(path, N, c_h*W + c_w)
print(dist[d_h*W+d_w])

"""

print(board)
que = deque([[c_h, c_w]])
visited = []
# bfs()
while que:
    h, w = que.popleft()
    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] == '.':  # セルが白('.')であるのと同義
            que.append((new_h, new_w))

    print(h, w)
"""


### 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)