/* -*- coding: utf-8 -*-
 *
 * 3193.cc:  No.3193 Submit Your Solution - yukicoder
 */

#include<cstdio>
#include<vector>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 200000;
const int BN = 18;

/* typedef */

using ull = unsigned long long;

struct Tree {
  const int n, BN;
  using vi = vector<int>;
  using vvi = vector<vi>;
  
  vvi nbrs, ps;
  vi cis, ds;

  Tree(int _n, int _BN):
    n(_n), BN(_BN), nbrs(n), ps(n, vi(BN)), cis(n, 0), ds(n) {
    for (int i = 1; i < n; i++) {
      int u, v;
      scanf("%d%d", &u, &v);
      u--, v--;
      nbrs[u].push_back(v);
      nbrs[v].push_back(u);
    }

    ps[0][0] = -1, ds[0] = 0;
    for (int u = 0; u >= 0;) {
      auto &nbru = nbrs[u];
      int up = ps[u][0];

      if (cis[u] < nbru.size()) {
	int v = nbru[cis[u]++];
	if (v != up) {
	  ps[v][0] = u, ds[v] = ds[u] + 1;
	  u = v;
	}
      }
      else {
	u = up;
      }
    }

    for (int i = 0; i < BN - 1; i++)
      for (int u = 0; u < n; u++)
	ps[u][i + 1] = (ps[u][i] >= 0) ? ps[ps[u][i]][i] : -1;
  }

  int find_lca(int u, int v) {
    if (ds[u] > ds[v]) swap(u, v);
    for (int i = BN - 1; i >= 0; i--)
      if (((ds[v] - ds[u]) >> i) & 1) v = ps[v][i];
    if (u == v) return u;

    for (int i = BN - 1; i >= 0; i--)
      if (ps[u][i] != ps[v][i])
	u = ps[u][i], v = ps[v][i];
    return ps[u][0];
  }

  int dist(int u, int v, int lca = -1) {
    if (lca < 0) lca = find_lca(u, v);
    return ds[u] + ds[v] - ds[lca] * 2;
  }
};

/* global variables */

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);

  Tree ta(n, BN), tb(n, BN);

  ull sum = 0;
  for (int p = 0; p < n; p++)
    for (int q = p + 1; q < n; q++)
      sum += (ull)ta.dist(p, q) * tb.dist(p, q) * 2;

  printf("%llu\n", sum);
  
  return 0;
}