/**
 *  When Can We Meet? (PKU 2028)
 *  by Kenji Inoue, 2006-12-22
 **/

#include <iostream>

using namespace std;

int main() {
  int n, q;
  int date[100];

  while (cin >> n >> q, (n || q)) {
    memset(date, 0, sizeof(date)); // initialize with 0s

    for (int i=0; i<n; i++) {
      int m;
      cin >> m;
      for (int j=0; j<m; j++) {
        int d;
        cin >> d;
        date[d]++;
      }
    }

    int maxi = 0;
    for (int i=1; i<100; i++) {
      if (date[i] > date[maxi]) { maxi = i; }
    }

    if (date[maxi] >= q) {
      cout << maxi << endl;
    } else {
      cout << 0 << endl;
    }
  }

  return 0;
}