#include <iostream>
#include <cstring>
#include <algorithm>
#include <cstdio>
#include <iomanip>
#include <cmath>
#include <string>
#define MOD 1000000007
using namespace std;
struct line
{
	int y,next;
}e[200050];
int linkk[100050],n,q[100050],p[100050],a[100050];
long long f[100050],ans=0;
void init()
{
	cin>>n>>a[1];
	for (int i=2;i<=n;i++)
	{
		scanf("%d%d",&p[i],&a[i]);
		e[2*i-1].y=i;
		e[2*i-1].next=linkk[p[i]];
		linkk[p[i]]=2*i-1;
		e[2*i].y=p[i];
		e[2*i].next=linkk[i];
		linkk[i]=2*i;
	}
}
void dfs(int k)
{
	f[k]=a[k];
	for (int i=linkk[k];i;i=e[i].next)
		if (e[i].y!=p[k])
		{
			dfs(e[i].y);
			f[k]+=f[e[i].y];
			ans=(ans+f[e[i].y]%MOD*a[k]%MOD*a[k]%MOD*2%MOD)%MOD;
		}
	for (int i=linkk[k];i;i=e[i].next)
		if (e[i].y!=p[k])
			ans=(ans+(f[k]-a[k]-f[e[i].y])%MOD*(f[e[i].y]%MOD)%MOD*a[k]%MOD)%MOD;
}
int main()
{
	freopen("asm_algo.in","r",stdin);
	freopen("asm_algo.out","w",stdout);
	init();
	dfs(1);
	for (int i=1;i<=n;i++)
		ans=(ans+a[i]*a[i]%MOD*a[i]%MOD)%MOD;
	cout<<ans<<endl;
	fclose(stdin);
	fclose(stdout);
	return 0;
}