https://www.acwing.com/problem/content/1115/

#include<bits/stdc++.h>
using namespace std;
int dx[]={-1,1,0,0},dy[]={0,0,-1,1};
int flag[25][25]={0};
int n,m;
char china[25][25];
int dfs(int x,int y)
{
    flag[x][y]=1;
    int count=1;
    for(int i=0;i<4;i++)
    {
        int a=x+dx[i],b=y+dy[i];
        if(a<0||b<0||a>=n||b>=m)continue;
        if(china[a][b]=='#')continue;
        if(flag[a][b])continue;
        count+=dfs(a,b);
    }
    return count;
}
int main(){
    while(1){

    cin>>m>>n;
    if(m==0||n==0)break;
    memset(flag,0,sizeof flag);
    int x,y;
    for(int i=0;i<n;i++)
    for(int j=0;j<m;j++){
    cin>>china[i][j];
    if(china[i][j]=='@')x=i,y=j;
    }
    cout<<dfs(x,y)<<endl;
    }
    return 0;
}