func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long max_n = 1e6 + 20;   long long n, m, k, ans, sum;   long long a[max_n];   long long mark[max_n];   vector<long long> v, adj[max_n], jda[max_n];   void dfs(long long v) {     mark[v] = 1;     if (adj[v].size() == 2) ans = -1;     for (auto i : adj[v]) {       if (!mark[i]) {         dfs(i);       }     }   }   int32_t main() {     cin >> n;     for (long long i = 1; i < n; i++) {       long long u, v;       cin >> u >> v;       u--, v--;       adj[v].push_back(u);       adj[u].push_back(v);     }     if (n == 2) {       cout <<  YES ;       return 0;     }     for (long long i = 0; i < n; i++) {       if (adj[i].size() == 1 && !mark[i]) dfs(i);     }     if (ans == -1) {       cout <<  NO ;     } else       cout <<  YES ;     return 0;   }   