func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 1e6;   vector<int> gr[N];   long long int edges, z, o;   int col[N], vis[N];   void color(int n) {     for (int i = 0; i < gr[n].size(); i++) {       if (col[gr[n][i]] == -1) {         if (col[n] == 0) {           o++;           col[gr[n][i]] = 1;         } else {           z++;           col[gr[n][i]] = 0;         }         edges++;         color(gr[n][i]);       }     }   }   int main() {     int n, a, b;     cin >> n;     for (int i = 0; i < n - 1; i++) {       col[i] = -1;       cin >> a >> b;       gr[a].push_back(b);       gr[b].push_back(a);     }     col[n - 1] = -1;     col[n] = -1;     col[1] = 0;     z++;     color(1);     if (n == 1) {       cout << 0 << endl;     } else {       cout << z * o - edges << endl;     }     return 0;   }   