### BUGGY CODE ###

import sys


def input():
    return sys.stdin.readline().strip()


def main():
    h, w = [int(i) for i in input().split()]
    c_h, c_w = [int(i) for i in input().split()]
    d_h, d_w = [int(i) for i in input().split()]
    grid = [["#"] * (w + 2)]
    for _ in range(h):
        line = ["#"] + list(input()) + ["#"]
        grid.append(line)
    grid.append(["#"] * (w + 2))
    warp_count = [[float("inf")] * (w + 2) for _ in range(h + 2)]
    directions = ((1, 0), (-1, 0), (0, 1), (0, -1))

    stack = []
    warp_count[c_h][c_w] = 0
    stack.append((c_h, c_w, 0))

    while stack:
        _h, _w, warp = stack.pop()
        warp_count[_h][_w] = warp

        cnt = 0
        # walk
        for _a, _b in directions:
            if grid[_h + _a][_w + _b] != "#" and warp_count[_h + _a][_w + _b] > warp:
                cnt += 1
                stack.append((_h + _a, _w + _b, warp))

        if cnt == 4:  # 4方向行けるときにワープは不要
            continue

        # warp
        for x in range(-2, 3):
            for y in range(-2, 3):
                if (x, y) in directions:
                    continue
                elif x == 0 and y == 0:
                    continue
                elif _h + x < 0 or _h + x > h or _w + y < 0 or _w + y > w:
                    continue
                elif grid[_h + x][_w + y] == "#":
                    continue
                if warp_count[_h + x][_w + y] > warp + 1:
                    stack.append((_h + x, _w + y, warp + 1))

    if warp_count[d_h][d_w] == float("inf"):
        print(-1)
    else:
        print(warp_count[d_h][d_w])
    return


if __name__ == "__main__":
    main()


### FIXED CODE ###

import sys
from collections import deque


def input():
    return sys.stdin.readline().strip()


def main():
    INF = 10**7
    h, w = [int(i) for i in input().split()]
    c_h, c_w = [int(i) for i in input().split()]
    d_h, d_w = [int(i) for i in input().split()]
    grid = [["#"] * (w + 2)]
    for _ in range(h):
        line = ["#"] + list(input()) + ["#"]
        grid.append(line)
    grid.append(["#"] * (w + 2))
    warp_count = [[INF] * (w + 2) for _ in range(h + 2)]
    directions = ((1, 0), (-1, 0), (0, 1), (0, -1))
    warps = []
    for x in range(-2, 3):
        for y in range(-2, 3):
            if x == 0 and y == 0:
                continue
            if (x, y) not in directions:
                warps.append((x, y))

    stack = deque()
    warp_count[c_h][c_w] = 0
    stack.append((c_h, c_w, 0))

    while stack:
        _h, _w, warp = stack.pop()
        if warp > warp_count[_h][_w]:
            continue
        warp_count[_h][_w] = warp

        # walk
        for _a, _b in directions:
            if grid[_h + _a][_w + _b] != "#" and warp_count[_h + _a][_w + _b] > warp:
                stack.append((_h + _a, _w + _b, warp))

        # warp
        for x, y in warps:
            if _h + x < 0 or _h + x > h or _w + y < 0 or _w + y > w:
                continue
            elif grid[_h + x][_w + y] == "#":
                continue
            if warp_count[_h + x][_w + y] > warp + 1:
                stack.appendleft((_h + x, _w + y, warp + 1))

    if warp_count[d_h][d_w] == INF:
        print(-1)
    else:
        print(warp_count[d_h][d_w])
    return


if __name__ == "__main__":
    main()