from collections import deque
import sys

def main() -> None:
    sys.setrecursionlimit(1 << 25)
    input_data = sys.stdin.read().rstrip().splitlines()
    it = iter(input_data)

    H, W = map(int, next(it).split())
    Sy, Sx = map(int, next(it).split())   # 行, 列（1-indexed）
    Gy, Gx = map(int, next(it).split())   # 行, 列（1-indexed）

    Sy -= 1; Sx -= 1
    Gy -= 1; Gx -= 1

    grid = [list(next(it)) for _ in range(H)]

    DIRS  = [(1, 0), (-1, 0), (0, 1), (0, -1)]
    MASKS = [1 << i for i in range(4)]

    INF = -1
    dist = [[[INF] * 16 for _ in range(W)] for _ in range(H)]
    dq = deque()

    start_state = 0
    dist[Sy][Sx][start_state] = 0
    dq.append((Sy, Sx, start_state))

    while dq:
        y, x, state = dq.popleft()
        d_now = dist[y][x][state]

        if (y, x) == (Gy, Gx) and state == 0:
            print(d_now)
            return

        for k, (dy, dx) in enumerate(DIRS):
            ny, nx = y + dy, x + dx
            if 0 <= ny < H and 0 <= nx < W and grid[ny][nx] != '#':
                nstate = state ^ MASKS[k]       # 対応するビットを反転
                if dist[ny][nx][nstate] == INF:
                    dist[ny][nx][nstate] = d_now + 1
                    dq.append((ny, nx, nstate))

    print(-1)

if __name__ == "__main__":
    main()