func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 2e5 + 121;   int a[N], b[N], last[N], kol, ans, v, u, i, n;   inline void add(int v, int u) {     a[++kol] = u;     b[kol] = last[v];     last[v] = kol;   }   void dfs(int v, int p, int len) {     if (len == 2) {       ++ans;       return;     }     int x = last[v];     while (x) {       if (a[x] != p) dfs(a[x], v, len + 1);       x = b[x];     }   }   int main() {     cin >> n;     for (i = 1; i < n; ++i) {       cin >> v >> u;       add(v, u);       add(u, v);     }     for (i = 1; i <= n; ++i) dfs(i, 0, 0);     cout << ans / 2 << endl;   }   