func_code_string: #include <bits/stdc++.h>   using namespace std;   int i, j, k, n, m, l;   const int N = 1e5 + 8;   int vis[N];   vector<int> adj[N];   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     ;     cin >> n;     for (i = 1; i < n; i++) {       int u, v;       cin >> u >> v;       adj[u].push_back(v);       adj[v].push_back(u);     }     queue<int> q;     q.push(1);     memset(vis, 0, sizeof(vis));     vis[1] = 1;     l = 0;     long long ev = 0, od = 0;     while (1) {       int c = q.size();       if (!c) break;       while (c) {         int s = q.front();         q.pop();         c--;         if (l & 1)           ev++;         else           od++;         for (auto u : adj[s]) {           if (!vis[u]) {             vis[u] = 1;             q.push(u);           }         }       }       l++;     }     cout << (ev * od - (n - 1)) <<   n ;     return 0;   }   