#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<vector<int>> pos;
	vector<vector<int>> bind;
	vector<vector<int>> childs;
	
	centroid_tree(vector<vector<int>> argE){
		int n = argE.size();
		E.resize(n,vector<int>());

		cnt.resize(n);
		r = go(0,argE);
		
		pos.resize(n);
		bind.resize(n);
		childs.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){
		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;
			}
			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();
		bind[cur].push_back(childs[cur].size());
	}
	
};
struct lca{
	
	vector<int> depth;//depth[i] 頂点iの深さ
	vector<vector<int>> parents;//parents[i][j] 頂点iから2^j個上の親
	
	int max_j = 30;
	
	lca(int n,vector<vector<int>> &E){
		depth.assign(E.size(),-1);
		parents.assign(E.size(),vector<int>(max_j,-1));
		
		stack<int> s;
		s.push(n);
		depth[n] = 0;
		while(s.size()!=0){
			int k = s.top();
			s.pop();
			for(int i=0;i<E[k].size();i++){
				int x = E[k][i];
				if(depth[x]!=-1)continue;
				s.push(x);
				depth[x] = depth[k]+1;
				for(int j=0;j<max_j;j++){
					if(j==0){
						parents[x][j] = k;
					}
					else{
						parents[x][j] = parents[parents[x][j-1]][j-1];
					}
					if(parents[x][j] == -1)break;
				}
			}
		}
	}
	
	//頂点uのk番目の親
	int kth_parent(int u,int k){
		for(int i=0;i<max_j;i++){
			if(k==0)break;
			if(u==-1)break;
			if(k%2){
				u = parents[u][i];
			}
			k/=2;
		}
		return u;
	}
	
	int query(int u,int v){
		if(depth[u]<depth[v])swap(u,v);
		u = kth_parent(u,depth[u]-depth[v]);
		
		if(u==v){
			return u;
		}
		
		for(int i=max_j-1;i>=0;i--){
			if(parents[u][i]!=parents[v][i]){
				u = parents[u][i];
				v = parents[v][i];
			}
		}
		
		return parents[u][0];
		
	}
	
	int get_distance(int u,int v){
		return depth[u]+depth[v]-2*depth[query(u,v)];
	}
	
	
};
mint get_dis(lca &H,vector<mint> &S,int u,int v){
	int l = H.query(u,v);
	mint ret = S[u] + S[v] - S[l]*2;
	return ret;
}

int main(){
	
	int n;
	cin>>n;
	
	vector<vector<int>> E(n);
	vector<vector<pair<int,mint>>> E2(n);
	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].emplace_back(v,w);
		E2[v].emplace_back(u,w);
	}
	
	centroid_tree C(E);

	lca H(0,E);

	vector<mint> dis(n,0);
	vector<bool> visited(n,false);
	queue<int> Q;
	Q.push(0);
	visited[0] = true;
	while(Q.size()>0){
		int u = Q.front();
		Q.pop();
		rep(i,E2[u].size()){
			int v = E2[u][i].first;
			mint w = E2[u][i].second;
			if(visited[v])continue;
			visited[v] = true;
			dis[v] = dis[u] + w;
			Q.push(v);
		}
	}
	
	mint ans = 0;
	
	rep(i,n){
		mint sum = 0;
		mint temp = 0;
		int cur = 0;
		rep(j,C.childs[i].size()){
			mint d = get_dis(H,dis,i,C.childs[i][j]);
			ans += d*d * (C.bind[i].back() - (C.bind[i][cur+1] - C.bind[i][cur]));
			ans += d*2*sum;
			temp += d;
			if(j+1 == C.bind[i][cur+1]){
				cur++;
				sum += temp;
				temp = 0;
			}
		}
	}
	
	cout<<ans.val()<<endl;
	
    return 0;
}