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// Paweł Jasiak pj103199
// pj1031999@gmail.com

/******************* INCLUDE *******************/

#include <bits/stdc++.h>
using namespace std;

/****** tr1 extension ******/
#if __cplusplus < 201103LL
#include <bits/stdtr1c++.h>
using namespace tr1;
#endif

/****** GNU extension ******/
#ifdef EXT
#include <bits/extc++.h>
using namespace __gnu_cxx;
using namespace __gnu_pbds;
#endif

/******************* TYPEDEF *******************/

typedef vector<int> VI;
typedef long long LL;
typedef long double LD;
typedef vector<VI> VVI;
typedef vector<LL> VLL;
typedef vector<double> VD;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;
typedef vector<PII> VPII;
typedef vector<PLL> VPLL;

/******************* DEFINE *******************/

#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 FOREACHD(i, c) for (VAR(i, (c.rbegin())); i != (c).rend(); ++i)
#define WRITE(c) FOREACH(it, (c)) cout << (*it) << " ";

#define CLR(x, a) memset((x), (a), sizeof((x)))
#define eprintf(...) fprintf(stderr, __VA_ARGS__)

#define TIMESTAMP(x)                                                           \
  eprintf("[" #x "] Time = %.3lfs\n", clock() * 1.0 / CLOCKS_PER_SEC)

#define DBG(x) cerr << ">> " << #x << " = " << x << endl;

#define ___                                                                    \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(NULL);                                                               \
  cout.tie(NULL);

#define RAND(a, b) ((rand() % (b - a + 1)) + (a))
#define FLUSH()                                                                \
  fflush(stdout);                                                              \
  fflush(stderr);

#define HEAP priority_queue
#define PB push_back
#define ST first
#define ND second
#define PF push_front
#define MP make_pair

/******************* VARS *******************/

const int MOD = (int)1e9 + 7;
const int MOD2 = (int)1e9 + 9;

const int INF = 1000000001;
const long long LLINF = (long long)1e18 + 1;

const double EPS = 10e-9;

const int MAXN = (int)1e6 + 7;
const int MX = (int)500 + 7;

int n, m;

VI V[MX];
VI actual{1}, tmp;
VI wzor;

/******************* CODE *******************/

bool ok() {
  bool oks = true;
  for (int i = 0; i < actual.size(); ++i) {
    oks = true;
    for (int j = 0, k = i; j < wzor.size(); ++j, ++k) {
      if (k >= actual.size())
        return false;

      if (wzor[j] != actual[k])
        oks = false;

      if (!oks)
        break;
    }
    if (oks) return true;
  }
  return false;
}

int main(void) {
  scanf(" %d %d", &n, &m);

  FOR(i, 1, n) {
    int number;
    scanf("%d", &number);
    V[i].reserve(number);
    while (number--) {
      int tmps;
      scanf("%d", &tmps);
      V[i].PB(tmps);
    }
  }

  wzor.reserve(m);
  REP(i, m) {
    int tmps;
    scanf("%d", &tmps);
    wzor.PB(tmps);
  }

  int ile = 1;
  while (!ok()) {
    if (ile >= 20) {
      printf("-1\n");
      return 0;
    }
    tmp = actual;
    actual.clear();
    FOREACH(it, tmp)
    FOREACH(ptr, V[*it])
    actual.PB(*ptr);
    ++ile;
  }

  printf("%d\n", ile);

  return 0;
}