#!/usr/bin/ python3.8
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
from collections import deque

H, W = map(int, readline().split())
sx, sy = map(int, readline().split())
gx, gy = map(int, readline().split())
# sx = H + 1 - sx
# gx = H + 1 - gx

grid = [1] * (W + 2)
for _ in range(H):
    grid += [1] + [1 * (x == '#') for x in readline().rstrip().decode()] + [1]
grid += [1] * (W + 2)

H += 2
W += 2
N = H * W
S = sx * W + sy
G = gx * W + gy

INF = 10 ** 9
dist = [INF] * N
q = deque([S])
dist[S] = 0
dxs = (1, -1, W, -W)
while q:
    v = q.popleft()
    dw = dist[v] + 1
    for dx in dxs:
        w = v + dx
        if dist[w] <= dw or grid[w]:
            continue
        q.append(w)
        dist[w] = dw

print(dist[G])