### BUGGY CODE ###

import math
from itertools import product
from collections import deque

h, w = map(int, input().split())
c = tuple(map(lambda x: int(x) - 1, input().split()))
d = tuple(map(lambda x: int(x) - 1, input().split()))
S = {}
roads = set()
for i in range(h):
    s = input()
    for j in range(w):
        S[i, j] = s[j]
        if s[j] == '.':
            roads.add((i, j))

index = 0
section = {}
reached = {k: False for k in roads}

for p in roads:
    if reached[p]:
        continue
    else:
        reached[p] = True
        stack = [p]
        section[p] = index
        while stack:
            v = stack.pop()
            i, j = v
            adj = []
            if i > 0 and S[i - 1, j] == '.':
                adj.append((i-1, j))
            if j > 0 and S[i, j - 1] == '.':
                adj.append((i, j - 1))
            if i < h-1 and S[i + 1, j] == '.':
                adj.append((i+1, j))
            if j < w-1 and S[i, j+1] == '.':
                adj.append((i, j+1))
            for u in adj:
                if not reached[u]:
                    reached[u] = True
                    stack.append(u)
                    section[u] = index
        index += 1

# print(roads)
# print(section)
if section[c] == section[d]:
    print(0)
    exit(0)

vertex = range(index)
edges = {i: set() for i in vertex}
for i, j in roads:
    head = section[i, j]
    square = product(range(max(i-2, 0), min(i+3, h)),
                     range(max(j-2, 0), min(j+3, w)))
    for m in square:
        if S[m] == '.':
            tail = section[m]
            if tail != head and S[m] == '.':
                edges[tail].add(head)
                edges[head].add(tail)

source = section[c]
target = section[d]
distance = {v: math.inf for v in vertex}
distance[source] = 0
reached_ = {k: False for k in vertex}
reached_[source] = True
queue = deque([source])
while queue:
    u = queue.popleft()
    for v in edges[u]:
        if not reached_[v]:
            reached_[v] = True
            distance[v] = distance[u] + 1
            queue.append(v)

if distance[target] != math.inf:
    print(distance[target])
else:
    print(-1)



### FIXED CODE ###

import math
from itertools import product
from collections import deque

h, w = map(int, input().split())
ch, cw = map(lambda x: int(x) - 1, input().split())
dh, dw = map(lambda x: int(x) - 1, input().split())
S = [input() for _ in range(h)]


distance = [[math.inf for _ in range(w)] for _ in range(h)]
distance[ch][cw] = 0
queue = deque([(ch, cw)])
pathes = {(0, -1), (-1, 0), (0, 1), (1, 0)}
warps = set(product(range(-2, 3), range(-2, 3))) - {(0, 0)} - pathes

while queue:
    i, j = queue.popleft()
    for pi, pj in pathes:
        u, v = i+pi, j+pj
        if 0 <= u < h and 0 <= v < w and S[u][v] == '.' and distance[u][v] > distance[i][j]:
            distance[u][v] = distance[i][j]
            queue.appendleft((u, v))

    for wi, wj in warps:
        x, y = i + wi, j + wj
        if 0 <= x < h and 0 <= y < w and S[x][y] == '.' and distance[x][y] > distance[i][j] + 1:
            distance[x][y] = distance[i][j] + 1
            queue.append((x, y))

print(distance[dh][dw] if distance[dh][dw] != math.inf else -1)