#include<bits/stdc++.h>
using namespace std;
long long n,w[100005],hd[200005],nxt[200005],ver[200005],idx,s[100005],res;
void add(long long x,long long y){
    ver[++idx]=y;
    nxt[idx]=hd[x];
    hd[x]=idx;
}
long long dfs(long long x){
    long long sum=0;
    for (long long i=hd[x];i;i=nxt[i]){
        long long y=ver[i];
        sum+=dfs(y);
    }
    s[x]=sum+w[x];
    return s[x];
}
long long mul(long long x,long long y){
    return x*y%1000000007;
}
void getRes(long long p){
    long long sz=s[p];
    res+=mul(mul(w[p],w[p]),sz*2-w[p]);
    for (long long i=hd[p];i;i=nxt[i]){
        res+=mul(mul(s[ver[i]],sz-s[ver[i]]-w[p]),w[p]);
        getRes(ver[i]);
    }
    return;
}
int main(){
    freopen("asm_algo.in","r",stdin);
    freopen("asm_algo.out","w",stdout);
    scanf("%d%d",&n,&w[1]);
    for (long long i=2;i<=n;i++){
        long long x;
        scanf("%d%d",&x,&w[i]);
        add(x,i);
    }
    dfs(1);
    getRes(1);
    cout<<res%1000000007;
    return 0;
}