func_code_string: #include <bits/stdc++.h>   using namespace std;   vector<int> adj[100005], dir[100005], vec;   int vis1[100005], vis2[100005], vis3[100005], fl = 0;   void dfs1(int u) {     vis1[u] = 1;     vec.push_back(u);     for (int i = (int)0; i <= (int)adj[u].size() - 1; i++) {       if (!vis1[adj[u][i]]) dfs1(adj[u][i]);     }   }   void dfs2(int u) {     vis2[u] = 1;     vis3[u] = 1;     for (int i = (int)0; i <= (int)dir[u].size() - 1; i++) {       if (!vis2[dir[u][i]]) dfs2(dir[u][i]);       if (vis3[dir[u][i]]) fl = 1;     }     vis3[u] = 0;   }   int fun() {     int ret = 0;     for (int j = (int)0; j <= (int)vec.size() - 1; j++) {       if (!vis2[vec[j]]) {         fl = 0;         dfs2(vec[j]);         ret += fl;       }     }     return (ret == 0);   }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(0);     cout.tie(0);     int n, m;     cin >> n >> m;     for (int i = (int)1; i <= (int)m; i++) {       int u, v;       cin >> u >> v;       adj[u].push_back(v);       adj[v].push_back(u);       dir[u].push_back(v);     }     int ans = 0;     for (int i = (int)1; i <= (int)n; i++) {       if (!vis1[i]) {         vec.clear();         dfs1(i);         ans += vec.size() - fun();       }     }     cout << ans << endl;     return 0;   }   