### BUGGY CODE ###

import sys
import copy
from collections import deque

sys.setrecursionlimit(10**6)
input = sys.stdin.readline
#read = sys.stdin.buffer.read

digtmp = [(0, 1), (1, 0), (0, -1), (-1, 0)]
area = [
    (-2, -2), (-2, -1), (-2, 0), (-2, 1), (-2, 2),
    (-1, -2), (-1, -1), (-1, 0), (-1, 1), (-1, 2),
    (0, -2), (0, -1), (0, 1), (0, 2),
    (1, -2), (1, -1), (1, 0), (1, 1), (1, 2),
    (2, -2), (2, -1), (2, 0), (2, 1), (2, 2)
]

def warp(a:int, b:int, cnt:int):
    ans = []
    for i, j in area:
        x, y = a+i, b+j
        if 0 <= x < H and 0 <= y < W:
            if field[x][y] == '.' and check[x][y] == -1:
                ans.append((x, y))
    return ans


def main():
    global field, check, H, W
    H, W = map(int, input().split())
    Ch, Cw = map(int, input().split())
    Dh, Dw = map(int, input().split())

    field = []
    check = [[-1] * W for _ in range(H)] 
    for h in range(H):
        tmp = list(input()[:-1])
        field.append(tmp)
    
    
    cnt = 0
    que = deque([(Ch-1, Cw-1)])
    for i in range(H*W):
        # BFS
        magic = []
        for _ in range(H*W):
            a, b = que.popleft()
            check[a][b] = cnt
            magic.append((a, b))
            for dx, dy in digtmp:
                x = a + dx
                y = b + dy
                if not (0 <= x < H and 0 <= y < W):
                    continue
                if check[x][y] != -1 or field[x][y] == '#':
                    continue
                check[x][y] = cnt
                que.append((x, y))
            if len(que) == 0:
                break
        # magic
        quetmp = []
        for _ in range(H*W):
            a, b = magic.pop()
            tmp = warp(a, b, cnt)
            quetmp += tmp 
            if len(magic) == 0:
                break
        cnt += 1
        que = deque(quetmp)
        
        if check[Dh-1][Dw-1] != -1:
            print(check[Dh-1][Dw-1])
            return
        if len(que) == 0:
            print(check[Dh-1][Dw-1])
            return


if __name__ == "__main__":
    main()


### FIXED CODE ###

import sys
import copy
from collections import deque

sys.setrecursionlimit(10**6)
input = sys.stdin.readline
#read = sys.stdin.buffer.read

digtmp = [(0, 1), (1, 0), (0, -1), (-1, 0)]
area = [
    (-2, -2), (-2, -1), (-2, 0), (-2, 1), (-2, 2),
    (-1, -2), (-1, -1), (-1, 0), (-1, 1), (-1, 2),
    (0, -2), (0, -1), (0, 1), (0, 2),
    (1, -2), (1, -1), (1, 0), (1, 1), (1, 2),
    (2, -2), (2, -1), (2, 0), (2, 1), (2, 2)
]

def warp(a:int, b:int, cnt:int):
    ans = []
    for i, j in area:
        x, y = a+i, b+j
        if 0 <= x < H and 0 <= y < W:
            if field[x][y] == '.' and check[x][y] == -1:
                check[x][y] = cnt
                ans.append((x, y))
    return ans


def main():
    global field, check, H, W
    H, W = map(int, input().split())
    Ch, Cw = map(int, input().split())
    Dh, Dw = map(int, input().split())

    field = []
    check = [[-1] * W for _ in range(H)] 
    for h in range(H):
        tmp = list(input()[:-1])
        field.append(tmp)
    
    
    cnt = 0
    que = deque([(Ch-1, Cw-1)])
    for i in range(H*W):
        # BFS
        magic = []
        for _ in range(H*W):
            if len(que) == 0:
                break
            a, b = que.popleft()
            magic.append((a, b))
            for dx, dy in digtmp:
                x = a + dx
                y = b + dy
                if not (0 <= x < H and 0 <= y < W):
                    continue
                if check[x][y] != -1 or field[x][y] == '#':
                    continue
                check[x][y] = cnt
                que.append((x, y))

        # magic
        quetmp = []
        cnt += 1
        for _ in range(H*W):
            a, b = magic.pop()
            tmp = warp(a, b, cnt)
            quetmp += tmp 
            if len(magic) == 0:
                break
        que = deque(quetmp)
        
        if check[Dh-1][Dw-1] != -1:
            print(check[Dh-1][Dw-1])
            return
        if len(que) == 0:
            print(check[Dh-1][Dw-1])
            return


if __name__ == "__main__":
    main()