#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cmath>
using namespace std;
const long long maxn=1000000007;
int n,ki;
long long f[100010];
int main()
{
	freopen("three_squirrels.in","r",stdin);
	freopen("three_squirrels.out","w",stdout);
	memset(f,0,sizeof(f));
	f[0]=1;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		int m;
		cin>>m;
		for(int j=1;j<=m;j++)
		{
			int q;
			cin>>q;
			f[i]=(f[i]+f[q])%maxn;
		}
	}
	cout<<f[n]<<endl;
	fclose(stdin);
	fclose(stdout);
	return 0;
}