#include<bits/stdc++.h>
using namespace std;
int fx[4]={0,1,0,-1}; 
int fy[4]={1,0,-1,0};
struct Node{
    int x,y,step;
};
queue<Node> q; 
int m,n,sx,sy,zx,zy; 
char a[50][50];
int main(){
    cin>>m>>n;
    for(int i=1;i<=m;i++){
        for(int j=1;j<=n;j++){
            cin>>a[i][j];
            if(a[i][j]=='@') sx=i,sy=j; 
            if(a[i][j]=='*') zx=i,zy=j; 
        }
    }
    q.push({sx,sy,0}); 
    a[sx][sy]='#';
    while(!q.empty()){
        int x=q.front().x;
        int y=q.front().y;
        int step=q.front().step;
        for(int i=0;i<=3;i++){
            int tx=x+fx[i];
            int ty=y+fy[i];
            if(tx>=1&&tx<=m&&ty>=1&&ty<=n&&a[tx][ty]!='#'){
                if(tx==zx&&ty==zy){
                    cout<<step+1;
                    return 0; 
                }
                q.push({tx,ty,step+1});
                a[tx][ty]='#';
            } 
        }
        q.pop();
    } 
    cout<<-1;
    return 0;
}
 
/**************************************************************
	Problem: 1900
	User: linzihang
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2080 kb
****************************************************************/