#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,m,mp[100][100],sx,sy,ex,ey,minn=0x3f3f3f3f,step=0;
char a[100][100];
int dxd[]{0,0,-1,0,1};
int dyd[]{0,1,0,-1,0};
void dfs(int x,int y){
	if(x==ex && y==ey){
		minn=min(minn,step);
		return;
	}
	if(mp[x][y]<=step){
		return;
	}
	mp[x][y]=step;
	for(int i=1;i<=4;++i){
		int xx,yy;
		xx=x+dxd[i];
		yy=y+dyd[i];
		if(a[xx][yy]!='#'){
			a[xx][yy]='#';
			step++;
			dfs(xx,yy);
			step--;
			a[xx][yy]='.';
		}
	}
}

signed main(){
	cin>>n>>m;
	memset(a,'#',sizeof(a));
	memset(mp,0x3f,sizeof(mp));
	for(int i=1;i<=n;++i){
		for(int j=1;j<=m;++j){
			cin>>a[i][j];
			if(a[i][j]=='@')
				sx=i,sy=j;
			if(a[i][j]=='*')
				ex=i,ey=j;
		}
	}
	a[sx][sy]='#';
	dfs(sx,sy);
	if(minn==0x3f3f3f3f){
		cout<<-1;
	}
	else{
		cout<<minn;
	}
	return 0;
}