#include "cstdio"

#include "queue"

#include "cstring"

using namespace std;

#define maxn 1005

bool vis[maxn][maxn];

char map[maxn][maxn];

int n,m,dir[][]={-,,,,,-,,},sx,sy,ex,ey;

struct status

{

    int x,y,dep;

    status(int x,int y,int dep):x(x),y(y),dep(dep) {}

    bool operator < (const status &a) const {return dep>a.dep;}

};

int bfs()

{

   priority_queue<status> Q;Q.push(status(sx,sy,));

   vis[sx][sy]=true;

   while(!Q.empty())

   {

       status t=Q.top();Q.pop();

       for(int s=;s<;s++)

       {

           int X=t.x+dir[s][],Y=t.y+dir[s][];

           if(X<||X>n||Y<||Y>m||vis[X][Y]) continue;

           int cost=map[X][Y]=='.'?:;

           if(X==ex&&Y==ey) return t.dep+cost;

           vis[X][Y]=true;

           Q.push(status(X,Y,t.dep+cost));

       }

   }

   return -;

}

int main()

{

    //freopen("in.txt","r",stdin);

    while(scanf("%d%d",&n,&m)&&n)

    {

        memset(vis,,sizeof(vis));

        for (int i=;i<=n;i++) scanf("%s",map[i]+);

        scanf("%d%d%d%d",&sx,&sy,&ex,&ey);

        int ans=bfs();

        printf("%d\n",ans);

    }

}