from collections import deque

def main():
    h, w = map(int, input().split())
    ch, cw = map(int, input().split())
    ch -= 1
    cw -= 1
    dh, dw = map(int, input().split())
    dh -= 1
    dw -= 1
    maze = [input() for i in range(h)]
    visited = [[-1]*w for j in range(h)]
    
    def maze_solver(maze, visited, sy, sx, gy, gx):
        mv = [[1, 0], [-1, 0], [0, 1], [0, -1]]
        q = deque([[sy, sx]])
        visited[sy][sx] = 0 
        _yx = list()
        _yx.append([sy, sx])
        while q:
            y, x = q.popleft()
            if y == gy and x == gx:
                ans = visited[y][x]
                return ans, visited, _yx
            for i, j in mv:
                if (0 <= y + i < h) and (0 <= x + j < w):  
                    ny = y+i
                    nx = x+j
                    if visited[ny][nx] != -1:
                        continue
                    if maze[ny][nx] == '.':
                        visited[ny][nx] = visited[y][x] + 1 
                        q.append([ny, nx])
                        _yx.append([ny, nx])
                else:
                    continue
        _yx = list(map(list, set(map(tuple, _yx))))
        return -1, visited, _yx

    def telepo(visited, _yx, h, w):
        n_yx = list()
        for y, x in _yx:
            for ny in range(-2, 3):
                for nx in range(-2, 3):
                    if 0 < y+ny < h and \
                        0 < x+nx < w and \
                        visited[y+ny][x+nx] == -1 and \
                        maze[y+ny][x+nx] != '#': 
                        n_yx.append([y+ny, x+nx])
        n_yx_s = list(map(list, set(map(tuple, n_yx))))
        return n_yx_s
    
    telepo_cnt = 0
    ans, visited, _yx = maze_solver(maze, visited, ch, cw, dh, dw)
    if ans != -1:
        print(telepo_cnt)
        exit()
    else:
        n_yx_s = telepo(visited, _yx, h, w)
        while len(n_yx_s) > 0:
            telepo_cnt += 1
            for ny, nx in n_yx_s:
                ans, visted = maze_solver(maze, visited, ny, nx, dh, dw)
                if ans != -1:
                    print(telepo_cnt)
                    exit()
    print(-1)
                        
if __name__ == '__main__':
    main()

### FIXED CODE ###

def main():
    from collections import deque
    import sys
    input = sys.stdin.readline
    h, w = map(int, input().split())
    ch, cw = map(int, input().split())
    dh, dw = map(int, input().split())
    # 迷路の四方を##で囲む。
    # 移動で枠外にでてしまってindexがないことを阻止するための
    # if文を回避
    maze = ['#' * (w+4)]
    maze.append('#' * (w+4))
    for _ in range(h):
        maze.append('##' + input()[:-1] + '##')
    maze.append('#' * (w+4))
    maze.append('#' * (w+4))
    visited = [[-1] * (w+4) for _ in range(h+4)]
    for i in range(h+4):
        for j in range(w+4):
            if maze[i][j] == '#':
                visited[i][j] = -2
    # この条件ではindexを+1しないとダメ
    ch += 1
    cw += 1
    dh += 1
    dw += 1
    visited[ch][cw] = 0
    walk = [[1, 0], [-1, 0], [0, 1], [0, -1]]
    telepo = [[i,j] for i in range(-2, 3) for j in range(-2, 3)]

    q_walk = deque([[ch, cw]])
    q_telepo = deque([])
    while q_walk:
        yw, xw = q_walk.popleft()
        # 行った場所を管理
        q_telepo.append([yw, xw])
        for i, j in walk:
            ny, nx = yw + i, xw + j
            # if ny < 0 or h <= ny or nx < 0 or w <= nx:
            #     continue
            if visited[ny][nx] == -1:
                # 行ったことあれば0にしていく
                visited[ny][nx] = visited[yw][xw]
                q_walk.append([ny, nx])
        # 歩ける場所なくなったらワープ
        if len(q_walk) == 0:
            while q_telepo:
                yt, xt = q_telepo.popleft()
                for i, j in telepo:
                    my, mx = yt + i, xt + j
                    # if my < 0 or h <= my or mx < 0 or w <= mx:
                    #     continue
                    # 次がまだ行ったことないところだったら、今までの値に+1
                    # つまり、テレポートしないといけない場所
                    if visited[my][mx] == -1:
                        visited[my][mx] = visited[yt][xt] + 1
                        q_walk.append([my, mx])
    print(visited[dh][dw])

if __name__ == '__main__':
    main()