#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n) - 1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

using mint = modint1000000007;

void debug_mint1(vector<mint> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        cerr << vec[i].val() << " ";
    }
    cerr << endl;
}

void debug_mint2(vector<vector<mint>> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        for (int j = 0; j < vec[i].size(); j++) {
            cerr << vec[i][j].val() << " ";
        }
        cerr << endl;
    }
}

// 全方位木 DP の抽象化ライブラリ
// https://trap.jp/post/1702/
template <class E, class V, E (*merge)(E, E), E (*e)(), E (*put_edge)(V, int),
          V (*put_vertex)(E, int)>
struct RerootingDP {
    struct edge {
        int to, idx, xdi;
    };
    RerootingDP(int n_ = 0) : n(n_), inner_edge_id(0) {
        es.resize(2 * n - 2);
        start.resize(2 * n - 2);
        if (n == 1) es_build();
    }
    void add_edge(int u, int v, int idx, int xdi) {
        start[inner_edge_id] = u;
        es[inner_edge_id] = {v, idx, xdi};
        inner_edge_id++;
        start[inner_edge_id] = v;
        es[inner_edge_id] = {u, xdi, idx};
        inner_edge_id++;
        if (inner_edge_id == 2 * n - 2) {
            es_build();
        }
    }
    vector<V> build(int root_ = 0) {
        root = root_;
        vector<V> subdp(n);
        subdp[0] = put_vertex(e(), 0);
        outs.resize(n);
        vector<int> geta(n + 1, 0);
        for (int i = 0; i < n; i++) geta[i + 1] = start[i + 1] - start[i] - 1;
        geta[root + 1]++;
        for (int i = 0; i < n; i++) geta[i + 1] += geta[i];
        auto dfs = [&](auto sfs, int v, int f) -> void {
            E val = e();
            for (int i = start[v]; i < start[v + 1]; i++) {
                if (es[i].to == f) {
                    swap(es[start[v + 1] - 1], es[i]);
                }
                if (es[i].to == f) continue;
                sfs(sfs, es[i].to, v);
                E nval = put_edge(subdp[es[i].to], es[i].idx);
                outs[geta[v]++] = nval;
                val = merge(val, nval);
            }
            subdp[v] = put_vertex(val, v);
        };
        dfs(dfs, root, -1);
        return subdp;
    }
    vector<V> reroot() {
        vector<E> reverse_edge(n);
        reverse_edge[root] = e();
        vector<V> answers(n);
        auto dfs = [&](auto sfs, int v) -> void {
            int le = outs_start(v);
            int ri = outs_start(v + 1);
            int siz = ri - le;
            vector<E> rui(siz + 1);
            rui[siz] = e();
            for (int i = siz - 1; i >= 0; i--) {
                rui[i] = merge(outs[le + i], rui[i + 1]);
            }
            answers[v] = put_vertex(merge(rui[0], reverse_edge[v]), v);
            E lui = e();
            for (int i = 0; i < siz; i++) {
                V rdp = put_vertex(
                    merge(merge(lui, rui[i + 1]), reverse_edge[v]), v);
                reverse_edge[es[start[v] + i].to] =
                    put_edge(rdp, es[start[v] + i].xdi);
                lui = merge(lui, outs[le + i]);
                sfs(sfs, es[start[v] + i].to);
            }
        };
        dfs(dfs, root);
        return answers;
    }

   private:
    int n, root, inner_edge_id;
    vector<E> outs;
    vector<edge> es;
    vector<int> start;
    int outs_start(int v) {
        int res = start[v] - v;
        if (root < v) res++;
        return res;
    }
    void es_build() {
        vector<edge> nes(2 * n - 2);
        vector<int> nstart(n + 2, 0);
        for (int i = 0; i < 2 * n - 2; i++) nstart[start[i] + 2]++;
        for (int i = 0; i < n; i++) nstart[i + 1] += nstart[i];
        for (int i = 0; i < 2 * n - 2; i++) nes[nstart[start[i] + 1]++] = es[i];
        swap(es, nes);
        swap(start, nstart);
    }
};

vector<ll> w;

struct E{
    mint sum_sq;
    mint sum;
    ll size;
};

struct V{
    mint sum_sq;
    mint sum;
    ll size;
};

E merge(E a, E b){
    return E{a.sum_sq + b.sum_sq, a.sum + b.sum, a.size + b.size};
}

E e(){
    return E{0, 0, 0};
}

E put_edge(V x, int i){
    mint new_sum_sq = x.sum_sq + 2 * x.sum * mint(w[i]) + mint(w[i]) * mint(w[i]) * mint(x.size);
    mint new_sum = x.sum + mint(w[i]) * mint(x.size);
    return E{new_sum_sq, new_sum, x.size};
}

V put_vertex(E x, int v){
    return V{x.sum_sq, x.sum, x.size + 1};
}

int main() {
    ll N;
    cin >> N;
    vector<ll> u(N - 1);
    vector<ll> v(N - 1);
    w.resize(N - 1);
    rep(i, N - 1){
        cin >> u[i] >> v[i] >> w[i];
        u[i]--;
        v[i]--;
    }
    RerootingDP<E, V, merge, e, put_edge, put_vertex> treedp(N);
    for (int i = 0; i < N - 1; i++){
        treedp.add_edge(u[i], v[i], i, i);
    }
    treedp.build();

    mint ans = mint(0);
    vector<V> ans_vec = treedp.reroot();
    for (ll i = 0; i < N; i++){
        ans += ans_vec[i].sum_sq;
    }
    ans /= mint(2);
    cout << ans.val() << endl;
}