R,C=map(int,input().split())
sx,sy=map(int,input().split())
gx,gy=map(int,input().split())
sx-=1
sy-=1
gx-=1
gy-=1

MAP=[input() for i in range(R)]
ANS=[[1<<31]*(C) for i in range(R)]

from collections import deque

Q=deque()
Q.append((sx,sy))
ANS[sx][sy]=0

while Q:
    x,y=Q.popleft()

    for w,z in [[x+1,y],[x-1,y],[x,y+1],[x,y-1]]:
        if 0<=w<R and 0<=z<C:
            if ANS[w][z]>ANS[x][y]+1:
                ANS[w][z]=ANS[x][y]+1
                Q.append((w,z))

print(ANS[gx][gy])