#include <bits/stdc++.h>
#define whlie while
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define rep(i,N) for(int i = 0; i < (N); i++)
#define repr(i,N) for(int i = (N) - 1; i >= 0; i--)
#define rep1(i,N) for(int i = 1; i <= (N) ; i++)
#define repr1(i,N) for(int i = (N) ; i > 0 ; i--)
#define each(x,v) for(auto& x : v)
#define all(v) (v).begin(),(v).end()
#define sz(v) ((int)(v).size())
#define vrep(v,it) for(auto it = v.begin(); it != v.end(); it++)
#define vrepr(v,it) for(auto it = v.rbegin(); it != v.rend(); it++)
#define ini(...) int __VA_ARGS__; in(__VA_ARGS__)
#define inl(...) ll __VA_ARGS__; in(__VA_ARGS__)
#define ins(...) string __VA_ARGS__; in(__VA_ARGS__)
#define rand rng
using namespace std; void solve();
using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using vvi = vector< vector<int> >;
constexpr int inf = 1001001001;
constexpr ll infLL = (1LL << 61) - 1;
mt19937_64 rng(58);
struct IoSetupNya {IoSetupNya() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); cerr << fixed << setprecision(7);} } iosetupnya;
template<typename T, typename U> inline bool amin(T &x, U y) { return (y < x) ? (x = y, true) : false; }
template<typename T, typename U> inline bool amax(T &x, U y) { return (x < y) ? (x = y, true) : false; }
template<typename T, typename U> ostream& operator <<(ostream& os, const pair<T, U> &p) { os << p.first << " " << p.second; return os; }
template<typename T, typename U> istream& operator >>(istream& is, pair<T, U> &p) { is >> p.first >> p.second; return is; }
template<typename T> ostream& operator <<(ostream& os, const vector<T> &v) { int s = (int)v.size(); rep(i,s) os << (i ? " " : "") << v[i]; return os; }
template<typename T> istream& operator >>(istream& is, vector<T> &v) { for(auto &x : v) is >> x; return is; }
void in(){} template <typename T,class... U> void in(T &t,U &...u){ cin >> t; in(u...);}
void out(){cout << "\n";} template <typename T,class... U> void out(const T &t,const U &...u){ cout << t; if(sizeof...(u)) cout << " "; out(u...);}
template<typename T>void die(T x){out(x); exit(0);}
#ifdef NyaanDebug
  #include "NyaanDebug.h"
  #define trc(...) do { cerr << #__VA_ARGS__ << " = "; dbg_out(__VA_ARGS__);} while(0)
  #define trca(v,N) do { cerr << #v << " = "; array_out(v , N);cout << endl;} while(0)
  int main(){solve_dbg();}
#else
  #define trc(...)
  #define trca(...)
  int main(){solve();}
#endif

using P = pair<ll,ll>;
constexpr int MOD = 998244853;

/////////

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

  edge(int to) : src(-1) , to(to) , cost(0){}
  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) { // edge e = n; とできる(e.to = n)
    to = x;
    return *this;
  }

  // int()をオーバーロードすることで重み付きグラフと普通のグラフでライブラリを共用できる
  operator int() const { return to; } // v[e]とできる ( v[e.to]に同じ )

};

// sort用 とりあえずcostの小さいほうが左としているが適宜書き換えて使いましょう
/**/
template<typename T>
bool operator <(const edge<T>& e1,const edge<T>& e2){ 
  return e1.to < e2.to;
}//*/
template< typename T >
using Edges = vector< edge< T > >;
template< typename T >
using WG = vector< Edges< T > >;
template< typename T>
using UWG = vector< vector <int> >;

int N;
WG<int> g;
ll ans = 0;
vi dp;
int dfs(int cur , int par){
  dp[cur] = 1;
  each(x , g[cur]){
    if(par == x) continue;
    int nodes = dfs(x , cur);
    ans += 1LL * x.cost * nodes * (N - nodes);
    dp[cur] += nodes;
  }
  return dp[cur];
}

void solve(){
  in(N);
  g.resize(N);
  rep(hoge , N - 1){
    ini(i , j , d); i--; j--;
    g[i].eb(j , d);
    g[j].eb(i , d);
  }
  dp.resize(N , 0);
  dfs(0 , -1); 
  out(ans * 2LL);
}