#include<bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
typedef long long ll;
using namespace std;
typedef pair<int,int> pii;

const int mod=1e9+7;
inline int add(int x,int y){int ret=x+y;if(ret>=mod)ret-=mod;return ret;}
inline int sub(int x,int y){int ret=x-y;if(ret<0)ret+=mod;return ret;}
inline int mul(int x,int y){return ((ll)x*y)%mod;}
inline int step(int base,int pw){int ret=1;while(pw){if(pw&1)ret=mul(ret,base);base=mul(base,base);pw>>=1;}return ret;}
inline int invv(int x){return step(x,mod-2);}


const int maxn=310;

struct polyn{

    vector<int>a;

    int size(){return a.size();}
    void resize(int x){a.resize(x);}
    int & operator [](int x){
        if(x>=a.size())resize(x+1);
        return a[x];
    }

    polyn operator *(polyn b){

        polyn ret;

        for(int i=0;i<size();i++)
            for(int j=0;j<b.size();j++)
            ret[i+j]=add(ret[i+j],mul(a[i],b[j]));

        return ret;
    }
    polyn operator *(int c){
        polyn ret=(*this);
        for(int i=0;i<ret.size();i++)
            ret[i]=mul(ret[i],c);
        return ret;
    }

    polyn operator +(int c){
        polyn ret=(*this);
        ret[0]=add(ret[0],c);
        return ret;
    }


    polyn integral(){
        polyn ret;
        for(int i=size();i>0;i--)
            ret[i]=mul(a[i-1],invv(i));
        return ret;
    }

    int eval(int x){
        int ret=0;
        int curr=1;
        for(int i=0;i<size();i++){
            ret=add(ret,mul(a[i],curr));
            curr=mul(curr,x);
        }
        return ret;
    }

    polyn mins(){
        polyn ret=(*this);
        for(int i=0;i<ret.size();i++)ret[i]=sub(0,ret[i]);
        return ret;
    }

    void ispis(){
        for(int i=0;i<a.size();i++){
            printf("%d ",a[i]);
        }
        printf("POLY ");
    }

};

struct sint{

    vector<pair<int,polyn>>a;

    int size(){return a.size();}

    pair<int,polyn>& operator [](int x){
        return a[x];
    }

    void pb(pair<int,polyn>c){
        a.pb(c);
    }

    sint operator *(sint b){

        sint ret;

        int pta=0;
        int ptb=0;

        while(pta<a.size() && ptb<b.size()){
            ret.pb({min(a[pta].ff,b[ptb].ff),a[pta].ss*b[ptb].ss});
            if(a[pta].ff==b[ptb].ff){pta++;ptb++;}
            else if(a[pta].ff<b[ptb].ff)pta++;
            else ptb++;
        }
        int eva=a.back().ss.eval(a.back().ff);
        int evb=b.a.back().ss.eval(b.a.back().ff);
        while(pta<a.size())ret.pb({a[pta].ff,a[pta++].ss*evb});
        while(ptb<b.size())ret.pb({b[ptb].ff,b[ptb++].ss*eva});

        return ret;
    }

    sint obrni(){

        sint ret=(*this);

        //printf("OBRNI\n");
        //ret[0].ss.ispis();

        int cc=a.back().ss.eval(a.back().ff);
        for(int i=0;i<a.size();i++){
            polyn pom=a[i].ss.mins()+cc;
            ret[i].ss=pom;
        }

        //ret[0].ss.ispis();
        //printf("OBRNI KRAJ\n");

        return ret;
    }

    void ispis(){

        for(int i=0;i<a.size();i++){
            printf("%d | ",a[i].ff);
            a[i].ss.ispis();
            printf("\n");
        }

    }

}f[maxn];

int n,b[maxn],p[maxn];
vector<int>vect[maxn];

void go(int x){

    //printf("AAAFE %d\n",x);

    int child=0;
    for(int i=0;i<vect[x].size();i++){
        int id=vect[x][i];
        go(id);
        child++;
        if(child==1){
            f[x]=f[id].obrni();
        }
        else f[x]=f[x]*f[id].obrni();

        //f[x].ispis();
    }

    //printf("AAA %d\n",x);

    if(child==0){
        polyn pom;
        pom[1]=invv(b[x]);
        f[x].pb({b[x],pom});
    }
    else{

        sint ret;

        //f[x].ispis();

        int prv=0;
        int sum=0;
        int invb=invv(b[x]);
        for(int i=0;i<f[x].size();i++){

            polyn itg=f[x][i].ss.integral();

            ret.pb({f[x][i].ff, (itg+sub(sum,itg.eval(prv)))*invb });

            sum=add(sum,sub(itg.eval(f[x][i].ff),itg.eval(prv) ) );

            prv=f[x][i].ff;
        }

        f[x]=ret;

        while(f[x].size()>=2 && f[x].a[f[x].size()-2].ff>=b[x])f[x].a.pop_back();
        f[x].a[f[x].size()-1].ff=min(f[x].a[f[x].size()-1].ff,b[x]);

        ///f[x].ispis();
    }

}

int main(){

    ///freopen("test.txt","r",stdin);

    scanf("%d",&n);
    int root=0;
    for(int i=1;i<=n;i++){
        scanf("%d %d",&b[i],&p[i]);
        if(p[i]!=0)vect[p[i]].pb(i);
        else root=i;
    }

    go(root);

    printf("%d\n",f[root].a.back().ss.eval(f[root].a.back().ff));

    return 0;
}