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#include <cstdio>
#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <queue>


/* PA-2015 R5 */
/* Korzystałem z kodu zaczęrpniętego z książki Piotr Stańczyka "Algorytmika Praktyczna" - kmp */
using namespace std;

typedef vector<int> VI;
typedef long long LL;

#define FOR(x, b, e) for(int x = b; x <= (e); ++x)
#define FORD(x, b, e) for(int x = b; x >= (e); --x)
#define REP(x, n) for(int x = 0; x < (n); ++x)
#define VAR(v, n) __typeof(n) v = (n)
#define ALL(c) (c).begin(), (c).end()
#define SIZE(x) ((int)(x).size())
#define FOREACH(i, c) for(VAR(i, (c).begin()); i != (c).end(); ++i)
#define PB push_back
#define ST first
#define ND second
#include <list>


bool found = false;

void xx(int)
{
	found = true;
}

void KMP(int* str, int strlen, int* wzo, int wzolen, void (*fun)(int)) { 
#define KMPH(z) while(k > 0 && wzo[k] != z[q]) k = p[k]; if(wzo[k] == z[q]) k++;
	LL p[wzolen + 1], k = 0, q, m;
	p[1] = 0;
	for (q = 1; q < wzolen; q++) {
		KMPH(wzo);
		p[q + 1] = k;
	}
	m = q;
	k = 0;
	for (q = 0; q < strlen; q++) {
		KMPH(str);
		if(m == k) {
			fun(q - m + 1); 
			k = p[k];
		}
	}
}


vector <int> nn[510];

int main ()
{
	int pat[1010];
	int n, m;
	scanf("%d %d", &n, &m);

	REP(i, n)
	{
		int cnt;
		scanf("%d", &cnt);

		REP(k, cnt)
		{
			int elem;
			scanf("%d", &elem);
			nn[i].PB(elem - 1);
		}
	}

	REP(i, m)
	{
		int elem;
		scanf("%d", &elem);
		pat[i] = elem - 1;
	}
	
	
  std::list<int> li;
  std::list<int>::iterator it;
  std::list<int>::iterator itb;

	li.PB(0);

int u = 0;
while(1)
{
	for(it = li.begin(); it != li.end(); ++it)
	{
		int elem = *it;

		itb = it;
		li.insert(it, nn[elem].begin(), nn[elem].end());
		--it;
		li.erase(itb);
	}	

	vector<int> test (li.begin(), li.end());

	KMP(test.data(), test.size(), &pat[0], m, xx);
	if(found)
	{
		cout<< u + 2 << endl;
		return 0;
	}

	if(li.size() > 15000000)
	{
		cout<< -1 << endl;
		return 0;
	}

	u++;
}






  return 0;
}