/**
	author:  shobonvip
	created: 2025.06.27 21:35:34
**/

#include<bits/stdc++.h>
using namespace std;

//* ATCODER
#include<atcoder/all>
using namespace atcoder;
typedef modint998244353 mint;
//*/

/* BOOST MULTIPRECISION
#include<boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
//*/

typedef long long ll;

#define rep(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
#define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--)
#define all(v) v.begin(), v.end()

template <typename T> bool chmin(T &a, const T &b) {
	if (a <= b) return false;
	a = b;
	return true;
}

template <typename T> bool chmax(T &a, const T &b) {
	if (a >= b) return false;
	a = b;
	return true;
}

template <typename T> T max(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmax(ret, a[i]);
	return ret;
}

template <typename T> T min(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmin(ret, a[i]);
	return ret;
}

template <typename T> T sum(vector<T> &a){
	T ret = 0;
	for (int i=0; i<(int)a.size(); i++) ret += a[i];
	return ret;
}

typedef unsigned long long ull;
int f1[200001],f2[200001],g1[400001],g2[400001];
ull d1[200001],d2[200001],ans=0;
int mada[999999];
bool seen[999999];

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	
	int n; cin >> n;
	vector<int> u(n-1), v(n-1), x(n-1), y(n-1);
	vector ikeru1(n, vector<int>(0));
	vector ikeru2(n, vector<int>(0));

	rep(i,0,n-1) {
		cin >> u[i] >> v[i];
		u[i]--; v[i]--;
		ikeru1[u[i]].push_back(v[i]);
		ikeru1[v[i]].push_back(u[i]);
	}
	rep(i,0,n-1) {
		cin >> x[i] >> y[i];
		x[i]--; y[i]--;
		ikeru2[x[i]].push_back(y[i]);
		ikeru2[y[i]].push_back(x[i]);
	}

	{
		int piv = 0;
		rep(i,0,n) {
			for (int x: ikeru1[i]) {
				g1[piv++] = x;
			}
			f1[i+1] = piv;
		}
	}
	{
		int piv = 0;
		rep(i,0,n) {
			for (int x: ikeru2[i]) {
				g2[piv++] = x;
			}
			f2[i+1] = piv;
		}
	}

	rep(st,0,n) {

		{
			fill(seen,seen+n,false);
			int piv = 1;
			mada[0] = st;
			seen[st] = 1;
			d1[st] = 0;
			while (piv > 0) {
				int i = mada[--piv];
				rep(x,f1[i],f1[i+1]){
					int j = g1[x];
					if (!seen[j]) {
						d1[j] = d1[i] + 1;
						mada[piv++] = j;
						seen[j] = 1;
					}
				}
			}
		}
		{
			fill(seen,seen+n,false);
			int piv = 1;
			mada[0] = st;
			seen[st] = 1;
			d2[st] = 0;
			while (piv > 0) {
				int i = mada[--piv];
				rep(x,f2[i],f2[i+1]){
					int j = g2[x];
					if (!seen[j]) {
						d2[j] = d2[i] + 1;
						mada[piv++] = j;
						seen[j] = 1;
					}
				}
			}
		}
		

		rep(i,st+1,n){
			ans += d1[i] * d2[i];
		}

	}

	ans *= 2;
	cout << ans << endl;

}