mod = 998244353


def main():
    import sys
    from bisect import bisect_left
    from collections import deque
    input = sys.stdin.readline

    H, W = map(int, input().split())
    sh, sw, gh, gw = map(int, input().split())
    gh -= 1
    gw -= 1
    G = []
    for _ in range(H):
        G.append(input().rstrip('\n'))

    R = []
    for w in range(W):
        col = []
        for h in range(H):
            if G[h][w] == ".":
                col.append(h)
        R.append(col)

    que = deque()
    seen = [[-1] * W for _ in range(H)]
    for w in range(W):
        que.append((0, 0, w))
        seen[0][w] = 0
    while que:
        x, h, w = que.popleft()
        if seen[h][w] < x:
            continue
        #print(x, h, w)

        # normal jump
        if w - 1 >= 0:
            j = bisect_left(R[w - 1], h+2) - 1
            h_back = R[w - 1][j]
            if seen[h_back][w - 1] == -1 or seen[h_back][w - 1] > x:
                seen[h_back][w - 1] = x
                que.appendleft((x, h_back, w - 1))
        if w + 1 < W:
            j = bisect_left(R[w + 1], h+2) - 1
            h_back = R[w + 1][j]
            if seen[h_back][w + 1] == -1 or seen[h_back][w + 1] > x:
                seen[h_back][w + 1] = x
                que.appendleft((x, h_back, w + 1))
        if w - 2 >= 0:
            j = bisect_left(R[w - 1], h+2) - 1
            h_back = R[w - 1][j]
            h_new = h_back + max(0, h - h_back) // 2 + 1
            jj = bisect_left(R[w - 2], h_new + 1) - 1
            hh = R[w - 2][jj]
            if seen[hh][w - 2] == -1 or seen[hh][w - 2] > x:
                seen[hh][w - 2] = x
                que.appendleft((x, hh, w - 2))
        if w + 2 < W:
            j = bisect_left(R[w + 1], h + 2) - 1
            h_back = R[w + 1][j]
            h_new = h_back + max(0, h - h_back) // 2 + 1
            jj = bisect_left(R[w + 2], h_new + 1) - 1
            hh = R[w + 2][jj]
            if seen[hh][w + 2] == -1 or seen[hh][w + 2] > x:
                seen[hh][w + 2] = x
                que.appendleft((x, hh, w + 2))

        # super jump
        if w - 2 >= 0:
            h_new = h + 1
            jj = bisect_left(R[w - 2], h_new + 1) - 1
            hh = R[w - 2][jj]
            if seen[hh][w - 2] == -1:
                seen[hh][w - 2] = x + 1
                que.append((x + 1, hh, w - 2))
        if w + 2 < W:
            h_new = h + 1
            jj = bisect_left(R[w + 2], h_new + 1) - 1
            hh = R[w + 2][jj]
            if seen[hh][w + 2] == -1:
                seen[hh][w + 2] = x + 1
                que.append((x + 1, hh, w + 2))
        h_new = h + 1
        jj = bisect_left(R[w], h_new + 1) - 1
        hh = R[w][jj]
        if seen[hh][w] == -1:
            seen[hh][w] = x + 1
            que.append((x + 1, hh, w))

    print(seen[gh][gw])
    #for h in range(H):
    #    print(*seen[h])


if __name__ == '__main__':
    main()