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#include <iostream>
#include <cstdio>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <vector>
#include <algorithm>

using namespace std;

bool isSubset(vector<int> A, vector<int> B){
		sort(A.begin(), A.end());
		sort(B.begin(), B.end());
		return includes(A.begin(), A.end(), B.begin(), B.end());
}


int main(){

	int n;
	int m;
	scanf("%d%d", &n,&m);

	vector< vector <int> > cells;
	for(int i = 0; i < n; ++i){
		vector <int> a;
		int l;
		scanf("%d", &l);
		for(int j = 0; j < l; ++j){
			int k;
			scanf("%d", &k);
			a.push_back(k);
		}
		cells.push_back(a);
	}


	vector<int> wantedSequence;
	for(int i = 0; i < m; ++i){
		int k;
		scanf("%d", &k);
		wantedSequence.push_back(k);
	}

	vector<int> currentSequence;
	currentSequence.push_back(1);


	for(long long result = 1; result < 15; ++result){
		if(isSubset(currentSequence, wantedSequence)){
						printf("%lld", result);
						return 0;
		}
		vector<int> newSequence;
		for(int i = 0; i < currentSequence.size(); ++i){
				for(int j = 0; j < cells[currentSequence[i] - 1].size(); ++j){
					newSequence.push_back(cells[currentSequence[i] - 1][j]);
				}
			}
			currentSequence = newSequence;
	}
	int a = -1;
	printf("%d\n", a);
	return 0;
}