from collections import deque
r,c=map(int,input().split())
sy,sx=map(int,input().split())
gy,gx=map(int,input().split())
sy-=1;sx-=1;gy-=1;gx-=1
g=[input() for _ in range(r)]
d=[[-1]*c for _ in range(r)]
q=deque()
d[sy][sx]=0
q.append((sy,sx))
while q:
    y,x=q.popleft()
    dy=[0,1,0,-1]
    dx=[1,0,-1,0]
    for i in range(4):
        ny=y+dy[i];nx=x+dx[i]
        if 0<=ny<r and 0<=nx<c:
            if d[ny][nx]==-1 and g[ny][nx]=='.':
                d[ny][nx]=d[y][x]+1
                q.append((ny,nx))
print(d[gy][gx])