#include<cstdlib>
#include<algorithm>
#include<cstring>
#include<string>
#include<string.h>
#include<vector>
#include<queue>
#include<cmath>
#include<cstdio>
#include<iostream>
using namespace std;
const long long pi=1000000007;
int m,n,w[10005],p[10005],f[1005][1005];
long long ans=0;
int find(int x,int y)
{
	if(p[x]=p[y])
	return w[p[x]];
	else {
		find(p[x],y);
		find(p[y],x);
		find(p[x],p[y]);
	}
}
int main()
{
	freopen("asm_algo.in","r",stdin);
	freopen("asm_algo.out","w",stdout);
	cin>>n>>w[1];
	for(int i=2;i<=n;i++)
	cin>>p[i]>>w[i];
	for(int i=1;i<=n;i++)
	for(int jj=1;jj<=n;jj++)
	{
		if(i==jj)f[i][jj]=f[jj][i]=w[i];
		else f[i][jj]=f[jj][i]=find(i,jj);
	}
	for(int i=1;i<=n;i++)
	for(int jj=1;jj<=n;jj++)
	{
		ans+=w[i]*w[jj]*f[i][jj]%pi;
	}
    cout<<ans<<endl;
    return 0;
}