### BUGGY CODE ###

from collections import deque


def bfs():
    H, W = map(int, input().split())
    C = list(map(int, input().split()))
    D = list(map(int, input().split()))
    S = [list(input()) for _ in range(H)]

    tests = (0, 1), (1, 0), (-1, 0), (0, -1)
    warps = (
        (1, 1),
        (-1, 1),
        (-1, -1),
        (1, -1),
        (2, 0),
        (2, -1),
        (2, -2),
        (1, -2),
        (0, -2),
        (-1, -2),
        (-2, -2),
        (-2, -1),
        (-2, 0),
        (-2, 1),
        (-2, 2),
        (-1, 2),
        (0, 2),
        (1, 2),
        (2, 2),
        (1, 2),
    )

    start = (0, C[0] - 1, C[1] - 1)
    goal = (D[0] - 1, D[1] - 1)

    queue = deque()
    # (ワープ回数, x, y)
    queue.append(start)

    while queue:
        # print(queue)
        w_n, x, y = queue.pop()

        # if x == goal[0] and y == goal[1]:
            #break

        # 通常移動
        for dx, dy in tests:
            nx = x + dx
            ny = y + dy

            if nx < 0 or nx >= H or ny < 0 or ny >= W:
                continue

            if S[nx][ny] != "#":
                if S[nx][ny] != "." and w_n >= S[nx][ny]:
                    continue
                else:
                    S[nx][ny] = w_n
                    queue.appendleft((w_n, nx, ny))

        # warp
        w_n += 1
        for dx, dy in warps:
            nx = x + dx
            ny = y + dy

            if nx < 0 or nx >= H or ny < 0 or ny >= W:
                continue

            if S[nx][ny] != "#":
                if S[nx][ny] != "." and w_n >= S[nx][ny]:
                    continue
                else:
                    S[nx][ny] = w_n
                    queue.append((w_n, nx, ny))


    if S[goal[0]][goal[1]] == ".":
        print(-1)
    else:
        print(S[goal[0]][goal[1]])

    # for h in range(H):
    #     print(S[h])


bfs()


### FIXED CODE ###

from collections import deque
import itertools


def bfs():
    H, W = map(int, input().split())
    C = list(map(int, input().split()))
    D = list(map(int, input().split()))
    S = [list(input()) for _ in range(H)]

    tests = (0, 1), (1, 0), (-1, 0), (0, -1)
    # warps = itertools.product(range(-2, 3), range(-2, 3))

    start = (0, C[0] - 1, C[1] - 1)
    goal = (D[0] - 1, D[1] - 1)

    queue = deque()
    # (ワープ回数, x, y)
    queue.append(start)

    while queue:
        w_n, x, y = queue.popleft()

        # 通常移動
        for dx, dy in tests:
            nx = x + dx
            ny = y + dy

            if not (0 <= nx < H):
                continue

            if not (0 <= ny < W):
                continue

            if S[nx][ny] != "#":
                if S[nx][ny] != "." and w_n >= S[nx][ny]:
                    continue
                else:
                    S[nx][ny] = w_n
                    queue.appendleft((w_n, nx, ny))

        # warp
        for dx, dy in itertools.product(range(-2, 3), range(-2, 3)):
            nx = x + dx
            ny = y + dy

            if not (0 <= nx < H):
                continue

            if not (0 <= ny < W):
                continue

            if S[nx][ny] != "#":
                if S[nx][ny] != "." and w_n + 1 >= S[nx][ny]:
                    continue
                else:
                    S[nx][ny] = w_n + 1
                    queue.append((w_n + 1, nx, ny))

    if S[goal[0]][goal[1]] == ".":
        print(-1)
    else:
        print(S[goal[0]][goal[1]])


bfs()