#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define MAXN 1000010
#define mod 1000000007
inline ll read(){
	ll x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9'){
		if(c=='-')f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		x=x*10+c-'0';
		c=getchar();
	}
	return x*f;
}
ll n,idx;
ll k[MAXN],siz[MAXN];
ll hd[MAXN],ed[MAXN],nxt[MAXN];
queue <ll> q;
void build(ll x,ll y){
	nxt[++idx]=hd[x];
	ed[idx]=y;
	hd[x]=idx;
}
int main(){
	freopen("three_squirrels.in","r",stdin);
	freopen("three_squirrels.out","w",stdout);
	n=read();
	for(int i=1;i<=n;i++){
		k[i]=read();
		for(int j=1;j<=k[i];j++){
			ll a=read();
			build(a,i);
		}
	}
	siz[0]=1;
	q.push(0);
	while(!q.empty()){
		ll fnt=q.front();
		q.pop();
		for(int i=hd[fnt];i;i=nxt[i]){
			ll y=ed[i];
			siz[y]=(siz[y]+siz[fnt])%mod;
			k[y]--;
			if(!k[y]){
				q.push(y);
			}
		}
	}
	cout<<siz[n];
	return 0;
}