func_code_string: #include <bits/stdc++.h>   using namespace std;   const unsigned long long hash1 = 201326611;   const unsigned long long hash2 = 50331653;   const int N = 200000 + 10;   const int M = 20;   vector<int> g[N];   int n, vis[N];   int main() {     ios::sync_with_stdio(false);     cin.tie(0), cout.tie(0);     cin >> n;     int u, v;     for (int i = 1; i < n; i++) {       cin >> u >> v;       vis[u]++;       vis[v]++;     }     int flag = 0;     for (int i = 1; i <= n; i++) {       if (vis[i] == 2) flag = 1;     }     if (flag)       cout <<  NO  << endl;     else       cout <<  YES  << endl;     return 0;   }   