#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define F first
#define S second
#define pii pair<int, int>
#define eb emplace_back
#define all(v) v.begin(), v.end()
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep3(i, l, n) for (int i = l; i < (n); ++i)
#define sz(v) (int)v.size()
#define inf (int)(1e9+7)
#define abs(x) (x >= 0 ? x : -(x))
#define ceil(a, b) a / b + !!(a % b)
ll pow(ll a, int b) { return b ? pow(a * a, b / 2) * (b % 2 ? a : 1) : 1; }
template<typename T> T gcd(T a, T b) { if (b == 0) return a; return gcd(b, a % b); }


int dist[200001];
vector<vector<pii> > v;
ll ans;
int n;

void dfs(int cur, int prev, int d) {
    for (auto nxt : v[cur]) {
        if (nxt.F == prev) continue;
        dfs(nxt.F, cur, nxt.S);
    }
    
    if (prev == -1) return;
    dist[prev] += dist[cur]; // 根ではいらない操作
    ans += 1LL * d * dist[cur] * (n - dist[cur]) * 2; // 根ではdist[cur] = 0
    
}

int main() {
    cin >> n;
    v.resize(n);
    rep(i, n) dist[i] = 1;
    
    rep(i, n - 1) {
        int u, vv, w;
        cin >> u >> vv >> w;
        u--; vv--;
        v[u].eb(make_pair(vv, w));
        v[vv].eb(make_pair(u, w));
    }
    
    dfs(0, -1, 0);
    cout << ans << endl;
}