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#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>
#include <stack>
#include <set>
#include <list>
#include <map>

using namespace std;

bool containsS(vector < int > State, vector < int > S)
{
    vector < int > Joined;
    for(int i = 0; i < S.size(); i++)
        Joined.push_back(S[i]);
    Joined.push_back(-1);
    for(int i = 0; i < State.size(); i++)
        Joined.push_back(State[i]);

    int n = Joined.size();
    vector < int > P(n);
    int t = 0;
    P[0] = 0; P[1] = 0;
    for(int i = 1; i < n; i++)
    {
        while (t > 0 && Joined[t] != Joined[i])
            t = P[t-1];
        if (Joined[t] == Joined[i])
            t++;
        P[i] = t;
    }

    for(int i = 0; i < P.size(); i++)
        if(P[i] == S.size())
            return 1;
    return 0;
}

int main()
{
    ios_base::sync_with_stdio(0);

    int n, m;
    cin >> n >> m;

    vector < vector < int > > V(n);

    for(int i = 0; i < n; i++)
    {
        int length;
        cin >> length;

        for(int j = 0; j < length; j++)
        {
            int a;
            cin >> a;
            a--;
            V[i].push_back(a);
        }
    }

    vector < int > S(m);

    for(int i = 0; i < m; i++)
    {
        int a;
        cin >> a;
        a--;
        S[i] = a;
    }

    vector < int > State(1, 0);
    vector < int > Tmp;
    int cnt = 1;

    while(!containsS(State, S))
    {
        for(int i = 0; i < State.size(); i++)
            for(int j = 0; j < V[State[i]].size(); j++)
                Tmp.push_back(V[State[i]][j]);

        State = Tmp;
        Tmp.resize(0);

        cnt++;

        if(cnt >= 10)
        {
            cout << -1;
            return 0;
        }
    }

    cout << cnt;

    return 0;
}