#include<iostream>
#include<cstdio>
using namespace std;
int k[100005],zi[100005][1005],u[100005],an[100005],n;
int ans(int x){
	if(an[x]!=0){
		return an[x];
	}
	if(x==0){
		return 1;
	}
	for(int i=1;i<=u[x];i++){
		an[x]=((an[x]%1000000007)+(ans(zi[x][i])%1000000007))%1000000007;
	}
	return (an[x]%1000000007);
}
int main(){
	freopen("three_squirrels.in","r",stdin);
	freopen("three_squirrels.out","w",stdout);
	int a,num=0;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>k[i];
		num=0;
		for(int j=1;j<=k[i];j++){
			cin>>a;
			zi[i][++num]=a;
		}
		u[i]=num;
	}
	cout<<ans(n);
	fclose(stdin);
	fclose(stdout); 
	return 0;
}