bitset<1>,启动！

#include<bits/stdc++.h>
using namespace std;
bitset<1> vis[10001];
vector<int>graph[10001];
int t,n,id,from,to,cnt;
void dfs(int x){
    for(int i=0;i<graph[x].size();++i){
        if(vis[graph[x][i]]==0){
            vis[graph[x][i]]=1;
            if(graph[x][i]!=id)cnt++;
            dfs(graph[x][i]);
        }
    }
}
int main(){
    scanf("%d",&t);
    for(int k=1;k<=t;++k){
        memset(vis,0,sizeof(vis));
        scanf("%d%d",&n,&id);
        for(int i=1;i<=10000;++i){
            graph[i].clear();
        }
        while(n--){
            scanf("%d%d",&to,&from);
            graph[from].push_back(to);
        }
        cnt=0;
        dfs(id);
        printf("Case #%d: %d\n",k,cnt);
    }
    return 0;
}