#include<bits/stdc++.h>
using namespace std;
#define inf INT_MAX
#define INF LLONG_MAX
#define ll long long
#define ull unsigned long long
#define M (int)(1e9+7)
#define P pair<int,int>
#define PLL pair<ll,ll>
#define FOR(i,m,n) for(int i=(int)m;i<(int)n;i++)
#define RFOR(i,m,n) for(int i=(int)m;i>=(int)n;i--)
#define rep(i,n) FOR(i,0,n)
#define rrep(i,n) RFOR(i,n,0)
#define all(a) a.begin(),a.end()
#define IN(a,n) rep(i,n){ cin>>a[i]; }
const int vx[4] = {0,1,0,-1};
const int vy[4] = {1,0,-1,0};
#define PI 3.14159265
#define F first
#define S second
#define PB push_back
#define EB emplace_back
#define int ll
#define vi vector<int>
#define IP pair<int,P>
#define PP pair<P,P>
#define Yes(f){cout<<(f?"Yes":"No")<<endl;}
#define YES(f){cout<<(f?"YES":"NO")<<endl;}



template< typename T >
struct edge {
  int src, to;
  T cost;

  edge(int to, T cost) : src(-1), to(to), cost(cost) {}

  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

  edge &operator=(const int &x) {
    to = x;
    return *this;
  }

  operator int() const { return to; }
};

template< typename T >
using Edges = vector< edge< T > >;
template< typename T >
using WG = vector< Edges< T > >;
using UG = vector< vector< int > >;
template< typename T >
using Matrix = vector< vector< T > >;

int n;
WG<int> es;
int ans=0;
vi v;

void dfs(int k,int p,int d){
  for(auto e:es[k]){
    if(e.to==p) continue;
    dfs(e.to,k,e.cost);
  }
  if(p==-1) return;
  v[p]+=v[k];
  ans+=d*v[k]*(n-v[k])*2;
}


signed main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout<<fixed<<setprecision(20);

  cin>>n;
  es=WG<int>(n);
  v=vi(n,1);
  rep(i,n-1){
    int a,b,c;
    cin>>a>>b>>c;
    a--;b--;
    es[a].PB(edge<int>(b,c));
    es[b].PB(edge<int>(a,c));
  }

  dfs(0,-1,-1);

  cout<<ans<<endl;


}