from collections import deque
import sys

R, C = map(int, input().split())

sx, sy = map(int, input().split())
gx, gy = map(int, input().split())
sy = sy-1
sx = sx-1
gy = gy-1
gx = gx-1
c = []

for i in range(R):
    r = list(input())
    c.append(r)

depth = 0
q = deque()
q.append([sx, sy, depth])
twd = [[1, 0], [0, 1], [-1, 0], [0, -1]]
visited = [([0] * C) for i in range(R)]


while q:
    x, y, d = q.popleft()
    for i in range(4):
        dx, dy = x + twd[i][0], y + twd[i][1]
        if (dx < 0) and (dx >= C):
            continue
        if (dy < 0) and (dy >= R):
            continue
        if c[dx][dy] == "#":
            continue
        if visited[dx][dy] == 1:
            continue
        q.append([dx, dy, d+1])
    visited[x][y] = 1
    if visited[gx][gy] == 1:
        print(d)
        sys.exit()