#include<bits/stdc++.h>
using namespace std;
using LL=long long;
using ULL=unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)

ULL M = 1000000007;

struct Mat{
    ULL S=0,L=0,C=0;
    void ad(){ *this={S,L,(C+1)%M}; }
    void ex(ULL d){ *this={(S+L*2*d%M+d*d%M*C)%M,(L+C*d)%M,C}; }
};

ULL sqsum(Mat l,Mat r){ return (l.S*r.C+l.L*2*r.L+r.S*l.C)%M; }
Mat mg(Mat l,Mat r){ return {(l.S+r.S)%M,(l.L+r.L)%M,(l.C+r.C)%M}; }

struct Edge{ int to; ULL d; };

int N;
vector<Edge> E[200000];
Edge P[200000]={};
vector<int> I;
Mat V[200000];
ULL ans=0;

int main(){
	cin>>N;
	rep(i,N-1){
		int u,v,d; cin>>u>>v>>d; u--; v--;
		E[u].push_back({v,d});
		E[v].push_back({u,d});
	}
	int pI=0;
	P[1]={-1,0}; I.push_back(1);
	while(I.size()>pI){
		int p=I[pI++];
		for(Edge e:E[p]) if(P[p].to!=e.to){ P[e.to]={p,e.d}; I.push_back(e.to); }
	}
	reverse(I.begin(),I.end());
	I.pop_back();

	for(int p:I){
		V[p].ad();
		V[p].ex(P[p].d);
		ans += sqsum(V[P[p].to],V[p]);
		ans += V[p].S;
		V[P[p].to] = mg(V[P[p].to],V[p]);
	}
	cout<<ans%M<<endl;
	return 0;
}