1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
#include <climits>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <vector>
using namespace std;

#define MAX_SIZE 1000000

vector<int> h[500 + 2];

bool kmp(const vector<int>& t, size_t expected_size) {
  vector<int> w(t.size() + 1, 0);
  w[0] = -1;

  for (long long i = 0, j = -1; i < t.size(); i++, j++, w[i] = j) {
    if (w[i] == expected_size) {
      return true;
    }
    while ((j >= 0) && (t[i] != t[j])) {
      j = w[j];
    }
  }
  return w[t.size()] == expected_size;
}

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

  for (int i = 1; i <= n; i++) {
    int l;
    scanf("%d", &l);
    for (int j = 0; j < l; j++) {
      int x;
      scanf("%d", &x);
      h[i].push_back(x);
    }
  }

  vector<int> S;
  for (int i = 0; i < m; i++) {
    int x;
    scanf("%d", &x);
    S.push_back(x);
  }

  if (S.size() == 1 && S[0] == 1) {
    printf("1\n");
    return 0;
  }

  vector<int> K, new_K;
  K.push_back(1);
  int iter = 2;

  while (new_K.size() < MAX_SIZE) {
    new_K = S;
    new_K.push_back(INT_MAX);
    for (size_t i = 0; i < K.size() && new_K.size() < MAX_SIZE; i++) {
      for (size_t j = 0; j < h[K[i]].size() && new_K.size() < MAX_SIZE; j++) {
        new_K.push_back(h[K[i]][j]);
      }
    }
    K.clear();
    //printf("Iter: %d, K: ", iter);
    for (size_t i = S.size() + 1; i < new_K.size(); i++) {
      K.push_back(new_K[i]);
    //  printf("%d ", K.back());
    }
    //printf("\n");
    
    if (kmp(new_K, S.size())) {
      printf("%d\n", iter);
      return 0;
    }

    iter++;
  }

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