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#include <iostream>
#include <vector>
#include <utility>
#include <queue>
#include <set>
#include <algorithm>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  vector<vector<int> > H(n);
  for (int i = 0; i < n; ++i) {
    int l;
    cin >> l;
    for (int j = 0; j < l; ++j) {
      int tmp;
      cin >> tmp;
      H[i].push_back(tmp);
    }
  }
  vector<int> S(m);
  for (int i = 0; i < m; ++i)
    cin >> S[i];

  vector<int> v = {1};
  int result = 1;
  int limit = 20;
  int cnt = 0;

  while (cnt <= limit) {
    if (search(v.begin(), v.end(), S.begin(), S.end()) != v.end()) { cout << result << endl; return 0; }
    vector<int> n;
    for (auto e : v) {
      n.insert(n.end(), H[e-1].begin(), H[e-1].end());
    }
    v = n;
    result++;
    cnt++;
  }


  cout << -1 << endl;

}