#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<ll, ll> p_ll;

template<class T>
void debug(T itr1, T itr2) { auto now = itr1; while(now<itr2) { cout << *now << " "; now++; } cout << endl; }
#define repr(i,from,to) for (ll i=(ll)from; i<(ll)to; i++)
#define all(vec) vec.begin(), vec.end()
#define rep(i,N) repr(i,0,N)
#define per(i,N) for (int i=(int)N-1; i>=0; i--)

const ll MOD = pow(10,9)+7;
const ll LLINF = pow(2,61)-1;
const int INF = pow(2,30)-1;

vector<ll> fac;
void c_fac(int x=pow(10,6)+10) { fac.resize(x,true); rep(i,x) fac[i] = i ? (fac[i-1]*i)%MOD : 1; }
ll inv(ll a, ll m=MOD) { ll b = m, x = 1, y = 0; while (b!=0) { int d = a/b; a -= b*d; swap(a,b); x -= y*d; swap(x,y); } return (x+m)%m; }
ll nck(ll n, ll k) { return fac[n]*inv(fac[k]*fac[n-k]%MOD)%MOD; }
ll gcd(ll a, ll b) { if (a<b) swap(a,b); return b==0 ? a : gcd(b, a%b); }
ll lcm(ll a, ll b) { return a/gcd(a,b)*b; }

struct edge { ll from, to, d; };
vector<vector<edge>> adj;
vector<ll> sz;

ll N;
ll result = 0;
void dfs(ll n=0, ll d=0, ll p=-1) {
  for (auto x: adj[n]) {
    if (x.to==p) continue;
    dfs(x.to,x.d,n);
    sz[n] += sz[x.to];
  }
  result += sz[n]*(N-sz[n])*d;
}

int main() {
  cin >> N;
  adj.resize(N);
  rep(i,N-1) {
    ll u, v, w; cin >> u >> v >> w; u--; v--;
    adj[u].push_back((edge){u,v,w});
    adj[v].push_back((edge){v,u,w});
  }
  sz.resize(N,1);
  dfs();

  result *= 2;
  cout << result << endl;
  return 0;
}