#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;

//template
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(a);i>(b);i--)
#define ALL(v) (v).begin(),(v).end()
typedef long long int ll; typedef pair<ll, ll> P;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<typename A,size_t N,typename T>void Fill(A(&array)[N],const T &val){fill((T*)array, (T*)(array+N), val);}
const int inf = INT_MAX / 2; const ll INF = LLONG_MAX / 2;
//template end

vector<vector<P>> g;
ll b[200010];
ll dfs(int v,int p){
    if(g[v].size()==0)return b[v]=1;
    ll res=1;
    for(P x:g[v])if(x.first!=p){
        res+=dfs(x.first,v);
    }
    return b[v]=res;
}

int main(){
    int n; scanf("%d",&n);
    g.resize(n); vector<pair<int,P>> es;
    rep(i,0,n-1){
        int u,v,w; scanf("%d%d%d",&u,&v,&w); u--; v--;
        g[u].push_back({v,w}); g[v].push_back({u,w});
        es.push_back({u,{v,w}});
    }
    ll ans=0; dfs(0,-1);
    rep(i,0,n-1){
        ll d=es[i].second.second;
        ll m=min(b[es[i].first],b[es[i].second.first]);
        ans+=m*(n-m)*d*2LL;
    }
    printf("%lld\n",ans);
    return 0;
}