### BUGGY CODE ###

import heapq
import sys


def input(): return sys.stdin.readline().rstrip()


H, W = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
data = [[0]*W for i in range(H)]

for i in range(H):
    S = input()
    for j in range(W):
        if S[j] == ".":
            data[i][j] = 1
        else:
            data[i][j] = 0


def trans(h, w):
    return W*(h) + w


P = [(0, -1), (0, 1), (1, 0), (-1, 0)]
DXY = [(i, j) for i in range(-2, 3) for j in range(-2, 3)]
G = [[] for i in range(H*W)]
H_L = [i for i in range(H)]
W_L = [i for i in range(W)]
for i in H_L:
    for j in W_L:
        if data[i][j] == 1:
            for dx, dy in P:
                if 0 <= dx+i < H:
                    if 0 <= dy+j < W:
                        if data[dx+i][dy+j] == 1:
                            u, v = trans(i, j), trans(dx+i, dy+j)
                            G[u].append((v, 0))
                            G[v].append((u, 0))
            for dx, dy in DXY:
                if 0 <= dx+i < H:
                    if 0 <= dy+j < W:
                        if data[dx+i][dy+j] == 1:
                            u, v = trans(i, j), trans(dx+i, dy+j)
                            G[u].append((v, 1))
                            G[v].append((u, 1))


D = [10**6+100 for i in range(H*W)]
D[trans(ch-1, cw-1)] = 0
que = []
heapq.heapify(que)
heapq.heappush(que, (0, trans(ch-1, cw-1)))

while que:
    cost, v = heapq.heappop(que)
    if D[v] < cost:
        continue
    for node, cost in G[v]:
        if D[node] > D[v] + cost:
            D[node] = D[v] + cost
            heapq.heappush(que, (D[node], node))

ans = D[trans(dh-1, dw-1)]

if ans == 10**6+100:
    print(-1)
else:
    print(ans)

### FIXED CODE ###

import heapq
import sys


def input(): return sys.stdin.readline().rstrip()


H, W = map(int, input().split())
ch, cw = map(int, input().split())
dh, dw = map(int, input().split())
data = [[0]*W for i in range(H)]

for i in range(H):
    S = input()
    for j in range(W):
        if S[j] == ".":
            data[i][j] = 1
        else:
            data[i][j] = 0


def trans(h, w):
    return W*(h) + w


P = [(0, -1), (0, 1), (1, 0), (-1, 0)]
DXY = []
for i in range(0, 3):
    for j in range(-2, 3):
        if i==0 and j==0:
            pass
        else:
            DXY.append((i,j))
            
G = [[] for i in range(H*W)]
H_L = [i for i in range(H)]
W_L = [i for i in range(W)]
for i in H_L:
    for j in W_L:
        if data[i][j] == 1:
            for dx, dy in P:
                if 0 <= dx+i < H and 0 <= dy+j < W and data[dx+i][dy+j] == 1:
                        u, v = trans(i, j), trans(dx+i, dy+j)
                        G[u].append((v, 0))
                        G[v].append((u, 0))
            for dx, dy in DXY:
                if 0 <= dx+i < H and 0 <= dy+j < W and data[dx+i][dy+j] == 1:
                        u, v = trans(i, j), trans(dx+i, dy+j)
                        G[u].append((v, 1))
                        G[v].append((u, 1))


D = [10**6+100 for i in range(H*W)]
D[trans(ch-1, cw-1)] = 0
que = []
heapq.heapify(que)
heapq.heappush(que, (0, trans(ch-1, cw-1)))

while que:
    cost, v = heapq.heappop(que)
    if D[v] < cost:
        continue
    for node, cost in G[v]:
        if D[node] > D[v] + cost:
            D[node] = D[v] + cost
            heapq.heappush(que, (D[node], node))

ans = D[trans(dh-1, dw-1)]

if ans == 10**6+100:
    print(-1)
else:
    print(ans)