#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<string>
using namespace std;
const int MAXN=1000000007;
int n,ans=0;
int a[1000000];
int main(){
	freopen("three_squirrels.in","r",stdin);
	freopen("three_squirrels.out","w",stdout);
	scanf("%d",&n);
	a[0]=1;
	for(int i=1;i<=n;i++){
		int m;
		scanf("%d",&m);
		for(int k=1;k<=m;k++){
			int y;
			scanf("%d",&y);
			a[i]+=a[y];
			a[i]%=MAXN;
		}
	}
	cout<<a[n]<<endl;
	return 0;
}