// Problem: P3905 道路重建
// Contest: Luogu
// URL: https://www.luogu.com.cn/problem/P3905
// Memory Limit: 125 MB
// Time Limit: 1000 ms
// Challenger: Erica N
// ----
// 
#include<bits/stdc++.h>

using namespace std;
#define rd read()
#define ull unsigned long long
#define int long long 
#define pb push_back
#define itn int
#define ps second 
#define pf first


#define rd read()
int read(){
  int xx = 0, ff = 1;char ch = getchar();
  while (ch < '0' || ch > '9'){
    if (ch == '-')ff = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9')xx = xx * 10 + (ch - '0'), ch = getchar();
  return xx * ff;
}
#define zerol = 1
#ifdef zerol
#define cdbg(x...) do { cerr << #x << " -> "; err(x); } while (0)
void err() {cerr << endl;}
template<template<typename...> class T, typename t, typename... A>
void err(T<t> a, A... x) {
	for (auto v: a) cerr << v << ' ';err(x...);
}
template<typename T, typename... A>
void err(T a, A... x) {
	cerr << a << ' ';err(x...);
}
#else
#define dbg(...)
#endif
const int N=2e6+5;
const ull P=137;
const int INF=1e18+7;
/*

策略


*/	



struct Node{
	int v,w;
};

vector<Node> e[N];

void add(int c,int b,int a){
	e[a].pb({b,c});
	e[b].pb({a,c});
}

int sz[N];
int n,ans;

int sum;

void dfs(int x,int fa){
	sz[x]=x;
	for(auto v:e[x]){
		if(v.v==fa)continue;
		dfs(v.v,x);
		sz[x]+=sz[v.v];
		ans+=(sz[v.v]*(sum-sz[v.v]))*v.w;
	}
}

signed main(){
	 n=rd;
	sum=(1+n)*n/2;
	for(int i=1;i<n;i++){
		add(1,rd,rd);
	}
	
	dfs(1,0);
	
	
	cout<<ans<<endl;
}