#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000000000000

struct centroid_tree{
	
	vector<vector<int>> E;
	vector<int> cnt;
	int r;
	
	vector<int> depth;
	vector<vector<int>> pos;
	vector<vector<int>> bind;
	vector<vector<int>> childs;
	vector<vector<int>> gs;
	
	centroid_tree(vector<vector<int>> argE){
		int n = argE.size();
		E.resize(n,vector<int>());

		cnt.resize(n);
		r = go(0,argE);
		
		depth.resize(n);
		pos.resize(n);
		bind.resize(n);
		childs.resize(n);
		gs.resize(n);
		dfs(r,-1,E);
		build(r,0);
		
	}
	
	int go(int a,vector<vector<int>> &argE){
		
		dfs(a,-1,argE);
		
		int sz = cnt[a];
		
		int ret = dfs2(a,-1,argE,sz);

		rep(i,argE[ret].size()){
			int to = argE[ret][i];
			argE[to].erase(find(argE[to].begin(),argE[to].end(),ret));
			
			int g = go(to,argE);
			E[ret].push_back(g);
		}
		argE[ret].clear();

		return ret;
		
	}
	
	void dfs(int cur,int p,vector<vector<int>> &argE){
		cnt[cur] = 1;
		rep(i,argE[cur].size()){
			int to = argE[cur][i];
			if(to==p)continue;
			dfs(to,cur,argE);
			cnt[cur] += cnt[to];
		}
	}
	
	int dfs2(int cur,int p,vector<vector<int>> &argE,int sz){
		int ret = -1;
		int m = 0;
		rep(i,argE[cur].size()){
			int to = argE[cur][i];
			if(to==p)continue;
			ret = dfs2(to,cur,argE,sz);
			if(ret!=-1)return ret;
			m = max(m,cnt[to]);
		}
		
		if(sz-cnt[cur]<=sz/2 && m<=sz/2){
			ret = cur;
		}
		return ret;
		
	}
	
	void build(int cur,int d){
		depth[cur] = d;
		bind[cur].push_back(0);
		rep(i,E[cur].size()){
			int to = E[cur][i];
			build(to,d+1);
			rep(j,childs[to].size()){
				int x = childs[to][j];
				childs[cur].push_back(x);
				if(pos[x].size()<=d)pos[x].resize(d+1,-1);
				pos[x][d] = i;
				if(gs[x].size()<=d)gs[x].resize(d+1,-1);
				gs[x][d] = cur;
			}
			bind[cur].push_back(childs[cur].size());
		}
		int x = cur;
		childs[cur].push_back(x);
		if(pos[x].size()<=d)pos[x].resize(d+1,-1);
		pos[x][d] = E[cur].size();
		if(gs[x].size()<=d)gs[x].resize(d+1,-1);
		gs[x][d] = cur;
		bind[cur].push_back(childs[cur].size());
	}
	
};

struct HLD{
	vector<int> sz,parent,depth,root,pos;
	vector<int> arr;
	HLD(vector<vector<int>> &E){
		sz.resize(E.size(),1);
		parent.resize(E.size(),0);
		depth.resize(E.size(),0);
		root.resize(E.size(),0);
		pos.resize(E.size(),0);
		
		dfs(0,-1,E);
		dfs2(0,-1,E,0);
	}
	
	void dfs(int now,int p,vector<vector<int>> &E){
		parent[now] = p;
		if(p==-1){
			depth[now] = 0;
		}
		else{
			depth[now] = depth[p]+1;
		}
		for(int i=0;i<E[now].size();i++){
			int to = E[now][i];
			if(to==p)continue;
			dfs(to,now,E);
			sz[now] += sz[to];
		}
	}
	
	void dfs2(int now,int p,vector<vector<int>> &E,int r){
		pos[now] = arr.size();
		arr.push_back(now);
		root[now] = r;
		int maxi = 0;
		int ind = -1;
		for(int i=0;i<E[now].size();i++){
			int to = E[now][i];
			if(to==p)continue;
			if(maxi<sz[to]){
				maxi = sz[to];
				ind = to;
			}
		}
		if(ind==-1)return;
		dfs2(ind,now,E,r);
		for(int i=0;i<E[now].size();i++){
			int to = E[now][i];
			if(to==p||to==ind)continue;
			dfs2(to,now,E,to);
		}
	}
	
	vector<pair<int,int>> query(int u,int v){
		vector<pair<int,int>> ret;
		int t = 0;
		while(root[u]!=root[v]){
			if(depth[root[u]] <= depth[root[v]]){
				ret.insert(ret.begin()+t,{pos[root[v]], pos[v]});
				v = parent[root[v]];
			}
			else{
				ret.insert(ret.begin()+t,{pos[u],pos[root[u]]});
				u = parent[root[u]];
				t++;
			}
		}
		ret.insert(ret.begin()+t,{pos[u],pos[v]});
		return ret;
	}
	
	int lca(int u,int v){
		for(;;v=parent[root[v]]){
			if(pos[u]>pos[v])swap(u,v);
			if(root[u]==root[v])return u;
		}
	}
	
	int get_distance(int u,int v){
		return depth[u] + depth[v] - 2 * depth[lca(u,v)];
	}
	
};

mint get_dis(HLD &H,vector<mint> &S,int u,int v){
	auto t = H.query(u,v);
	mint ret = 0;
	rep(i,t.size()){
		int l = t[i].first,r = t[i].second;
		if(l>r)swap(l,r);
		ret += S[r+1] - S[l];
	}
	return ret;
}

int main(){
	
	int n;
	cin>>n;
	
	vector<vector<int>> E(n);
	vector<vector<int>> E2(n*2-1);
	vector<mint> S(2*n,0);
	rep(i,n-1){
		int u,v,w;
		scanf("%d %d %d",&u,&v,&w);
		u--;v--;
		E[u].push_back(v);
		E[v].push_back(u);
		E2[u].push_back(n+i);
		E2[v].push_back(n+i);
		E2[n+i].push_back(u);
		E2[n+i].push_back(v);
		S[n+i] = w;
	}
	
	centroid_tree C(E);
	HLD H(E2);
	
	{
		vector<mint> SS(2*n,0);
		rep(i,2*n-1){
			SS[H.pos[i]+1] = S[i];
		}
		rep(i,2*n-1){
			SS[i+1] += SS[i];
		}
		swap(S,SS);
	}
	
	vector<vector<mint>> sum(n);
	
	rep(i,n){
		sum[i].push_back(0);
		rep(j,C.childs[i].size()){
			int u = C.childs[i][j];
			mint d = get_dis(H,S,i,u);
			sum[i].push_back(d);
		}
		rep(j,sum[i].size()){
			if(j==0)continue;
			sum[i][j] += sum[i][j-1];
		}
	}
	
	mint ans = 0;
	
	rep(i,n){
		rep(j,C.gs[i].size()){
			int x = C.gs[i][j];
			int l = C.bind[x][C.pos[i][j]];
			int r = C.bind[x][C.pos[i][j]+1];
			mint d = get_dis(H,S,i,x);
			ans += d*d * (C.bind[x].back() - (r-l));
			mint s = 0;
			s += sum[x].back() - sum[x][r];
			s += sum[x][l];
			ans += s*d;
		}
	}
	
	cout<<ans.val()<<endl;
	
    return 0;
}