func_code_string: #include <bits/stdc++.h>   using namespace std;   vector<vector<int> > g;   bitset<(int)1e6> us;   bool isCyclic(int v, int p = -1) {     us.set(v);     for (int i = 0; i < g[v].size(); i++) {       if (us.test(g[v][i]) && g[v][i] != p) return 0;       if (us.test(g[v][i])) continue;       bool cures = isCyclic(g[v][i], v);       if (!cures) return 0;     }     return 1;   }   int main() {     int n, m;     cin >> n >> m;     g.resize(n + 1);     for (int i = 0; i < m; i++) {       int v, to;       cin >> v >> to;       g[to].push_back(v);       g[v].push_back(to);     }     int sum = 0;     for (int i = 1; i <= n; i++) {       if (us.test(i)) continue;       sum += isCyclic(i);     }     cout << sum << endl;   }   