#include "bits/stdc++.h"
using namespace std;
#define int long long
#define FOR(i, a, b) for(int i=(a);i<(b);i++)
#define RFOR(i, a, b) for(int i=(b-1);i>=(a);i--)
#define REP(i, n) for(int i=0; i<(n); i++)
#define RREP(i, n) for(int i=(n-1); i>=0; i--)
#define REP1(i, n) for(int i=1; i<=(n); i++)
#define RREP1(i, n) for(int i=(n); i>=1; i--)
#define ALL(a) (a).begin(),(a).end()
#define UNIQUE_SORT(l) sort(ALL(l)); l.erase(unique(ALL(l)), l.end());
#define CONTAIN(a, b) find(ALL(a), (b)) != (a).end()
#define out(...) printf(__VA_ARGS__)

int dxy[] = {0, 1, 0, -1, 0};

void solve();
signed main()
{
#if DEBUG
    std::ifstream in("input.txt");
    std::cin.rdbuf(in.rdbuf());
#endif
    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}

/*================================*/
#if DEBUG
#define SIZE 100
#else
#define SIZE 223450
#endif

int N;

struct Edge {
    int src, to, w;
    Edge(int u, int v, int w): src(u), to(v), w(w) {};
};

vector< vector<Edge> > E(SIZE);
vector<Edge> F;
int W[SIZE];

void add_edge(int u, int v, int w) {
    E[u].push_back(*new Edge(u,v,w));
    E[v].push_back(*new Edge(v,u,w));
}

int dfs(int parent=-1, int i=0, int weight=0, int depth=0) {
    int ret = 1;
    for (auto e : E[i]) {
        if (e.to == parent) continue;
        ret += dfs(i, e.to, weight + e.w, depth+1);
    }
    return W[i] = ret;
}
/**********************************************************/


void solve() {
    cin>>N;
    int u,v,w;
    REP(i,N-1) {
        cin>>u>>v>>w;
        u--, v--;
        add_edge(u, v, w);
        F.push_back(*new Edge(u,v,w));
    }
    int total = dfs();
    int ans = 0;
    for (auto e:F) {
        int size = min(W[e.src], W[e.to]);
        ans += (total-size)*size*e.w*2;
    }
    
    cout << ans << endl;
}