- #include <cstdio>
- #include <vector>
- #include <cstring>
- using namespace std;
- int n,m,a,b;
- int book[10009],ans;
- vector <int> e[10009];
- int sum[10009];
- void dfs(int u,int s)
- {
- if(book[u]==1) return;
- book[u]=1;
- for(int i=0;i<e[u].size();i++)
- {
- int v=e[u][i];
- if(v!=s) sum[v]++;
- dfs(v,s);
- }
- return;
- }
- int main()
- {
-
- scanf("%d%d",&n,&m);
- for(int i=1;i<=m;i++)
- {
- scanf("%d%d",&a,&b);
- e[a].push_back(b);
- }
- for(int i=1;i<=n;i++)
- {
- memset(book,0,sizeof(book));
- dfs(i,i);
- }
- for(int i=1;i<=n;i++)
- {
- if(sum[i]==n-1)
- {
- ans++;
- }
- }
- printf("%d",ans);
- return 0;
- }
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