#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<string>
#include<cmath>
using namespace std;
struct N{
	int fa,w;
}tr[100100];
int n,w1;
N getfa(int x,int y)
{
	if (tr[x].fa==tr[y].fa)
	 return tr[tr[x].fa];
	else return getfa(tr[x].fa,tr[y].fa);
}
int main()
{
	freopen("asm_algo.in","r",stdin);
	freopen("asm_algo.out","w",stdout);
	cin>>n>>w1;
	tr[1].fa=1;
	tr[1].w=w1;
	for (int i=2;i<=n;i++)
	{
		cin>>tr[i].fa>>tr[i].w;
	}
	long long ans=0;
	for (int i=1;i<=n;i++) 
	 for (int j=1;j<=n;j++)
	 {
	 	if (i==j)
	 	{
	 		ans+=tr[i].w*tr[i].w*tr[i].w;
		}
		else 
	 	ans+=tr[i].w*tr[j].w*getfa(i,j).w;
	 	//cout<<getfa(i,j).fa<<"*"<<getfa(i,j).w<<endl;
	 	ans%=1000000007;
	 }
	cout<<ans;
	return 0; 
}