#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <sstream>
#include<set>
#include<stack>

//#include<bits/stdc++.h>


using namespace std;	
int n;
long long ans = 0;
vector<vector<pair<int, long long>>>p;
vector<long long>s;
void df(int cur, int prev, long long d) {
	for (int i = 0; i < p[cur].size(); i++) {
		int next = p[cur][i].first;
		if (next != prev)df(next, cur, p[cur][i].second);
	}
	if(prev == -1) return;
	s[prev] += s[cur];
	ans += d*s[cur] * (n - s[cur]) * 2;
}

int main() {


	cin >> n;
	
	p.resize(n);
	s.resize(n, 1);
	for (int i = 0; i < n-1; i++) {
		int a, b, d;
		cin >> a >> b >> d;
		a--; b--;
		p[a].push_back({b,d});
		p[b].push_back({a,d });
	}
	df(0, -1, -1);
	cout << ans << endl;

	return 0;




}