*red and black<pku 1979>

 // 额...很无聊做一些super大水题... 无聊逛网站发现今年acm final 在 Orlando<奥兰多> 进行 ，真是爽阿， 我等只能弱势围观，
　　 祝愿国内的众多神犇取得好成绩.
Source Code

Problem: 1979  User: eth1 
Memory: 736K  Time: 32MS 
Language: G++  Result: Accepted 

Source Code 
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <queue>
using namespace std;
int d[4][2]={-1,0,1,0,0,-1,0,1};
int ans,n,m,vis[21][21];
char f[21][21];
struct node{int x,y;};
queue<node> q;
bool check(node a)
{
    if(a.x<0 || a.x>=n || a.y<0 || a.y>=m || f[a.x][a.y]=='#' || vis[a.x][a.y])
    return 0;
    return 1;
}
void solve()
{
    while(!q.empty())
    {
        node a = q.front();
        q.pop();
        ans++;
        for(int i=0;i<4;i++)
        {
            node tem = a;
            tem.x += d[i][0];
            tem.y += d[i][1];
            if(check(tem))
            {
                vis[tem.x][tem.y]=1;
                q.push(tem);
            }
        }
    }
}
int main()
{
    while(cin>>m>>n && n+m)
    {
        int x,y;
        memset(vis,0,sizeof(vis));
        for(int i=0;i<n;i++)
        {
            cin>>f[i];
            for(int j=0;j<m;j++)
            {
                if(f[i][j]=='@')
                {
                    x=i;y=j;
                }
            }
        }
        vis[x][y]=1;
        node a;
        a.x=x;a.y=y;
        q.push(a);
        ans=0;
        solve();
        cout<<ans<<endl;
    }
    return 0;
}