40pts玄关

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll n,x,y,k,yy,edge_sum,head[100005],railway[100005];
bool vis[100005];
queue<ll>q;
struct edge{
	ll next,to;
}a[100005];
void add_edge(ll from,ll to){
	edge_sum++;
	a[edge_sum].next=head[from];
	a[edge_sum].to=to;
	head[from]=edge_sum;
}
void bfs(ll x){
	q.push(x);
	vis[x]=true;
	while(!q.empty()){
		ll t=q.front();
		q.pop();
		for(int i=head[t];i!=0;i=a[i].next)
		{
			if(vis[a[i].to])continue;
			if(a[i].to==y)return ;
			q.push(a[i].to);
			vis[a[i].to]=true;
			railway[a[i].to]=railway[t]+1;
		}
	}
	cout<<-1;
	exit(0);
}
signed main(){
	cin>>n>>x>>y;
	for(int i=1;i<=n;i++)
	{
		cin>>k;
		for(int j=1;j<=k;j++)
			cin>>yy,add_edge(i,yy);
	}
	bfs(x);
	cout<<railway[y];
	return 0;
}