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//brute
#include <cstdio>
#include <vector>

using std::printf;
using std::scanf;
using std::vector;

int n, m;
vector<int> transforms[501];
vector<int> sequence;
vector<int> bajtokomorczak;
vector<int> nowyBajtokomorczak;
int prefixes[1001];

void preKMP()
{
  prefixes[0] = -1;
  for (int i = 0; i < sequence.size(); i++) {
    prefixes[i + 1] = prefixes[i] + 1;
    while (prefixes[i + 1] > 0 && sequence[i] != sequence[prefixes[i + 1] - 1])
      prefixes[i + 1] = prefixes[prefixes[i + 1] - 1] + 1;
  }
}

bool kmp()
{
  for (int i = 0, j = 0; i < bajtokomorczak.size();) {
    if (j < 0 || bajtokomorczak[i] == sequence[j]) {
      ++i, ++j;
      if (j == sequence.size()) {
        return true;
      }
    }
    else j = prefixes[j];
  }
  return false;
}

int main()
{
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++)
  {
    int count;
    scanf("%d", &count);
    while (count--)
    {
      int next;
      scanf("%d", &next);
      transforms[i].push_back(next);
    }
  }

  for (int i = 0; i < m; i++)
  {
    int next;
    scanf("%d", &next);
    sequence.push_back(next);
  }

  preKMP();

  bajtokomorczak.push_back(1);
  for (int i = 1; i < 1000; i++)
  {
    if (kmp())
    {
      printf("%d\n", i);
      return 0;
    }
    nowyBajtokomorczak.clear();
    for (vector<int>::iterator it = bajtokomorczak.begin(); it != bajtokomorczak.end(); it++)
    {
      for (vector<int>::iterator it2 = transforms[*it].begin(); it2 != transforms[*it].end(); it2++)
        nowyBajtokomorczak.push_back(*it2);
    }
    bajtokomorczak = nowyBajtokomorczak;
  }

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