import sys
sys.setrecursionlimit(2147483647)
INF=float("inf")
MOD=10**9+7 # 998244353
input=lambda:sys.stdin.readline().rstrip()
from collections import deque
def resolve():
    h, w = map(int, input().split())
    si, sj = map(lambda x:int(x)-1, input().split())
    ti, tj = map(lambda x:int(x)-1, input().split())
    G = [input() for _ in range(h)]

    D = [(-1, 0), (1, 0), (0, -1), (0, 1)]
    dist = [[INF]*w for _ in range(h)]
    dist[si][sj] = 0
    Q = deque([(si, sj)])
    while Q:
        i, j = Q.popleft()
        for di, dj in D:
            ni, nj = i + di, j + dj
            if not (0 <= ni < h and 0 <= nj < w):
                continue
            if G[ni][nj] == '#':
                continue
            if dist[ni][nj] == INF:
                dist[ni][nj] = dist[i][j] + 1
                Q.append((ni, nj))

    print(dist[ti][tj])
resolve()