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//============================================================================
// Name        : .cpp
// Author      : Grzegorz Gajoch
// Description : 
//============================================================================

#include <cstdio>
#include <iostream>
#include <cstdlib>
#include <cmath>
#include <ctime>
#include <ctype.h>
#include <algorithm>
#include <string>
#include <string.h>
#include <cstring>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <list>

using namespace std;

#define FOR(i,a,b) for(int i = a; i <= b; ++i)
#define FORD(i,a,b) for(int i = a; i >= b; --i)
#define REP(x, n) for(int x=0; x < (n); ++x)
#define VAR(v,i) __typeof(i) v=(i)
#define FOREACH(i,c) for(VAR(i,(c).begin());i!=(c).end();++i)
#define SIZE(n) (int)n.size()
#define ALL(c) c.begin(),c.end()
#define PB(n) push_back(n)
typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<vector<int> > VVI;
typedef vector<bool> VB;
#define MP make_pair
#define ST first
#define ND second
const int INF = 1000000001;

//#define DEBUG
#ifdef DEBUG 
#define debug printf
#else
#define debug //
#endif

int N, S;
vector< vector<int> > Expensions;
vector<int> ending;

list < int > nowCell;

void clear() {
    nowCell.clear();
    nowCell.push_front(1);
    Expensions.clear();
    ending.clear();
}

void read() {
	scanf("%d %d", &N, &S);
    Expensions.resize(N+1);
    FOR(i, 1, N) {
        int len;
        scanf("%d", &len);
        REP(j, len) {
            int a;
            scanf("%d", &a);
            Expensions[i].push_back(a);
        }
    }
    REP(i, S) {
        int a;
        scanf("%d", &a);
        ending.push_back(a);
    }
}

void print() {
    debug("cell: ");
    FOREACH(itt, nowCell) {
        debug("%d ", *itt);
    }
    debug("\n");
}


vector<int> T;
void KMPPrep() {
    long long SeqLen = ending.size();
    T.resize(SeqLen + 1, -1);
    for(int i = 1; i <= SeqLen; i++)
    {
        int pos = T[i - 1];
        while(pos != -1 && ending[pos] != ending[i - 1])
            pos = T[pos];
        T[i] = pos + 1;
    }
}

bool checkForEnd() {
    //long long SigLen = SignalLength();
    long long AllLen = nowCell.size();
    long long SeqLen = ending.size();
    long long matches = 0;

    if( AllLen < SeqLen )
        return 0;

    int sp = 0;
    int kp = 0;
    list<int>::iterator it = nowCell.begin();
    while(sp < AllLen)
    {
        while(kp != -1 && (kp == SeqLen || ending[kp] != *it))
            kp = T[kp];
        kp++;
        sp++;
        it++;
        if(kp == SeqLen)
            return true;
            //matches++;
    }
    return false;
//    return matches;
}

int main(int argc, char **argv) {
    clear();
	read();
    KMPPrep();
    debug("A");
    long long counts = 0;
    FOR(xxxx, 1, 100000) { //100k iterations
		debug("iter: %d, len: %d\n",xxxx, nowCell.size());
		if( nowCell.size() > 2000000 ) {
			break;
		}
        list<int>::iterator it = nowCell.begin();
        while( it != nowCell.end() ) {
            int v = *it;
            debug("erasing: %d\n",v);
            //print();


            debug("adding: ");
            FOREACH(it2, Expensions[v]) {
                debug("%d ",*it2);
                nowCell.insert(it, *it2);
            }
            debug("\n");
            //print();
            auto rem = it;
            rem--;
            nowCell.erase(it);
            //print();
            debug("\n");debug("\n");

            it = rem;
            it++;
        }
        counts++;
        if( checkForEnd() ) {
            printf("%lld\n",counts+1);
            return 0;
        }

    }
	printf("-1\n");
    return 0;
}