### BUGGY CODE ###

import sys
import collections

sys.setrecursionlimit(10 ** 8)

input = sys.stdin.readline


def main():
    H, W = [int(x) for x in input().split()]
    CH, CW = [int(x) - 1 for x in input().split()]
    DH, DW = [int(x) - 1 for x in input().split()]
    S = [input().strip() for _ in range(H)]

    warp = ((-2, -2), (-2, -2), (-2, 0), (-2, 1), (-2, 2),
            (-1, -2), (-1, -1), (-1, 1), (-1, 2),
            (0, 2), (0, -2),
            (1, -2), (1, -1), (1, 1), (1, 2),
            (2, -2), (2, -1), (2, 0), (2, 1), (2, 2))

    visited = [[float("inf")] * W for _ in range(H)]

    q = collections.deque()
    visited[CH][CW] = 0
    q.append((CH, CW))
    while q:
        cx, cy = q.popleft()
        cc = visited[cx][cy]

        # 隣接
        kabe_cnt = 0
        for nx, ny in ([0, 1], [0, -1], [1, 0], [-1, 0]):
            nnx = cx + nx
            nny = cy + ny
            if 0 <= nnx <= H - 1 and 0 <= nny <= W - 1:
                if S[nnx][nny] == ".":
                    if visited[nnx][nny] > cc:
                        q.append((nnx, nny))
                        visited[nnx][nny] = cc
                else:
                    kabe_cnt += 1

        # ワープ
        if kabe_cnt > 0:
            for nx, ny in warp:
                nnx = cx + nx
                nny = cy + ny
                if 0 <= nnx <= H - 1 and 0 <= nny <= W - 1:
                    if S[nnx][nny] == "." and visited[nnx][nny] > cc:
                        q.append((nnx, nny))
                        visited[nnx][nny] = cc + 1

    if visited[DH][DW] == float("inf"):
        print(-1)
    else:
        print(visited[DH][DW])


if __name__ == '__main__':
    main()


### FIXED CODE ###

import sys
import collections

sys.setrecursionlimit(10 ** 8)

input = sys.stdin.readline


def main():
    H, W = [int(x) for x in input().split()]
    CH, CW = [int(x) - 1 for x in input().split()]
    DH, DW = [int(x) - 1 for x in input().split()]
    S = [input().strip() for _ in range(H)]

    warp = [[-2, -2], [-2, -1], [-2, 0], [-2, 1], [-2, 2],
            [-1, -2], [-1, -1], [-1, 1], [-1, 2],
            [0, 2], [0, -2],
            [1, -2], [1, -1], [1, 1], [1, 2],
            [2, -2], [2, -1], [2, 0], [2, 1], [2, 2]]

    visited = [[float("inf")] * W for _ in range(H)]

    q = collections.deque()
    visited[CH][CW] = 0
    q.append((CH, CW))
    while q:
        cx, cy = q.popleft()
        cc = visited[cx][cy]

        # 隣接
        kabe_cnt = 0
        for nx, ny in ([0, 1], [0, -1], [1, 0], [-1, 0]):
            nnx = cx + nx
            nny = cy + ny
            if 0 <= nnx <= H - 1 and 0 <= nny <= W - 1:
                if S[nnx][nny] == ".":
                    if visited[nnx][nny] > cc:
                        q.appendleft((nnx, nny))
                        visited[nnx][nny] = cc
                else:
                    kabe_cnt += 1

        # ワープ
        if kabe_cnt > 0:
            for nx, ny in warp:
                nnx = cx + nx
                nny = cy + ny
                if 0 <= nnx <= H - 1 and 0 <= nny <= W - 1:
                    if S[nnx][nny] == "." and visited[nnx][nny] > cc + 1:
                        q.append((nnx, nny))
                        visited[nnx][nny] = cc + 1

    if visited[DH][DW] == float("inf"):
        print(-1)
    else:
        print(visited[DH][DW])


if __name__ == '__main__':
    main()