import sys
from collections import deque
def input(): return sys.stdin.readline().rstrip()


def main():
    h, w = map(int, input().split())
    Ch, Cw = map(int, input().split())
    Dh, Dw = map(int, input().split())
    Ch -= 1
    Cw -= 1
    Dh -= 1
    Dw -= 1
    s2 = [list(input()) for i in range(h)]
    s2[Ch][Cw] = 0
    d = deque()
    d.append([Ch, Cw])
    while d:
        nowh, noww = d.popleft()
        for i, j in [[0, 1], [1, 0], [0, -1], [-1, 0]]:
            if ((0 <= nowh+i < h) and (0 <= noww+j < w)):
                if s2[nowh+i][noww+j] == '.':
                    s2[nowh+i][noww+j] = s2[nowh][noww]
                    d.appendleft([nowh+i, nowh+j])
                elif s2[nowh+i][noww+j] != '#':
                    if s2[nowh+i][noww+j] > s2[nowh][noww]:
                        s2[nowh+i][noww+j] = s2[nowh][noww]
                        d.append([nowh+i, noww+j])
        for i,j in [[-2,-2],[-2,-1],[-2,0],[-2,1],[-2,2],[-1,-2],[-1,-1],[-1,1],[-1,2],[0,-2],[0,2],[1,-2],[1,-1],[1,1],[1,2],[2,-2],[2,-1],[2,0],[2,1],[2,2]]:
            if ((0 <= nowh+i < h) and (0 <= noww+j < w)):
                if s2[nowh+i][noww+j] == '.':
                    s2[nowh+i][noww+j] = s2[nowh][noww]+1
                    d.append([nowh+i, noww+j])
                elif s2[nowh+i][noww+j] != '#':
                    if s2[nowh+i][noww+j] > s2[nowh][noww]+1:
                        s2[nowh+i][noww+j] = s2[nowh][noww]+1
                        d.append([nowh+i, noww+j])

    if s2[Dh][Dw] == '.':
        print(-1)
    else:
        print(s2[Dh][Dw])


if __name__ == '__main__':
    main()

### FIXED CODE ###

import sys
from collections import deque
def input(): return sys.stdin.readline().rstrip()
 
 
def main():
    h, w = map(int, input().split())
    Ch, Cw = map(int, input().split())
    Dh, Dw = map(int, input().split())
    Ch -= 1
    Cw -= 1
    Dh -= 1
    Dw -= 1
    s2 = [list(input()) for i in range(h)]
    s2[Ch][Cw] = 0
    d = deque()
    d.append([Ch, Cw])
    while d:
        nowh, noww = d.popleft()
        if [nowh,noww]==[Dh,Dw]:
            print(s2[nowh][noww])
            exit()
        for i, j in [[0, 1], [1, 0], [0, -1], [-1, 0]]:
            if ((0 <= nowh+i < h) and (0 <= noww+j < w)):
                if s2[nowh+i][noww+j] == '.':
                    s2[nowh+i][noww+j] = s2[nowh][noww]
                    d.appendleft([nowh+i, noww+j])
                elif s2[nowh+i][noww+j] != '#':
                    if s2[nowh+i][noww+j] > s2[nowh][noww]:
                        s2[nowh+i][noww+j] = s2[nowh][noww]
                        d.appendleft([nowh+i, noww+j])
        for i in [-2,-1,0,1,2]:
            for j in [-2,-1,0,1,2]:
                if ((0 <= nowh+i < h) and (0 <= noww+j < w)):
                    if s2[nowh+i][noww+j] == '.':
                        s2[nowh+i][noww+j] = s2[nowh][noww]+1
                        d.append([nowh+i, noww+j])
                    elif s2[nowh+i][noww+j] != '#':
                        if s2[nowh+i][noww+j] > s2[nowh][noww]+1:
                            s2[nowh+i][noww+j] = s2[nowh][noww]+1
                            d.append([nowh+i, noww+j])
    print(-1)
 
 
if __name__ == '__main__':
    main()