from collections import deque
INF = float("inf")

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)]
Q = deque([(si, sj, 0)])
while 1:
    i, j, d = 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 (ni, nj) == (ti, tj):
            print(d)
            exit(0)
        Q.append((di, dj, d + 1))