#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using mint = modint1000000007;
const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<long long,long long>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
struct ReRooting {
	struct Edge {//★★
		int to;
		mint cost;
		Edge(int _to, mint _cost) :to(_to), cost(_cost) {}
	};
	struct Data {//★★
		mint sump;
		mint sum;
		mint count;
		Data() :sump(0), sum(0), count(0) {}
		Data(mint _sump, mint _sum, mint _count) :sump(_sump), sum(_sum), count(_count) {}
	};
	vector<vector<Edge>>g;
	vector<Data>dp;
	vector<Data>dpR;
	int sz;
	ReRooting(int _sz) :sz(_sz) {
		g.resize(sz);
		dp.reserve(sz);
		dpR.resize(sz);
	}
	void ReadGraph() {//★★
		rep(i, sz - 1) {
			int a, b, c; cin >> a >> b >> c; a--; b--;
			g[a].push_back({ b,c });
			g[b].push_back({ a,c });
		}
	}
	Data merge(const Data &lh, const Data &rh, mint cost) {//★★
		Data ret = lh;
		ret.sump += rh.sump + rh.sum * cost * 2 + cost * cost * (rh.count + 1);
		ret.sum += rh.sum + cost * (rh.count + 1);
		ret.count += rh.count + 1;
		return ret;
	}
	Data mergeR(const Data &lh, const Data &rh, mint cost) {//★★
		Data ret = lh;
		ret.sump -= rh.sump + rh.sum * cost * 2 + cost * cost * (rh.count + 1);
		ret.sum -= rh.sum + cost * (rh.count + 1);
		ret.count -= rh.count + 1;
		return ret;
	}
	void dfs(int v, int p = -1) {
		Data val;
		for (auto e : g[v]) {
			if (p == e.to)continue;
			dfs(e.to, v);
			val = merge(val, dp[e.to], e.cost);
		}
		dp[v] = val;
	}
	void dfsR(int v, int p = -1, mint cost = 0) {
		dpR[v] = dp[v];
		if (-1 != p) {
			Data sub = mergeR(dpR[p], dp[v], cost);
			dpR[v] = merge(dpR[v], sub, cost);
		}
		for (auto e : g[v]) {
			if (p == e.to)continue;
			dfsR(e.to, v, e.cost);
		}
	}
	void output() {//★★
		mint ans = 0;
		rep(i, sz)ans += dpR[i].sump;
		ans *= inv_mod(2, mod);
		cout << ans.val() << endl;
	}
	void solve() {
		ReadGraph();
		dfs(0);
		dfsR(0);
		output();
	}
};
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	ReRooting reroot(n);
	reroot.solve();
	return 0;
}