func_code_string: #include <bits/stdc++.h>   using namespace std;   int ans;   int father[1100];   int find(int x) {     if (father[x] == x) return x;     father[x] = find(father[x]);     return father[x];   }   bool Union(int x, int y) {     int f1 = find(x);     int f2 = find(y);     if (f1 == f2) return false;     if (f1 < f2)       father[f1] = f2;     else       father[f2] = f1;     ans++;     return true;   }   int n, m;   int main() {     cin >> n >> m;     for (int i = 1; i <= n; i++) father[i] = i;     for (int i = 1; i <= m; i++) {       int x, y;       cin >> x >> y;       if (!Union(x, y)) {         cout <<  no  << endl;         return 0;       }     }     if (m != n - 1)       cout <<  no  << endl;     else       cout <<  yes  << endl;     return 0;   }   