/*!
  @file a.cc
  @brief Solves "When Can We Meet?" ( http://www.u-aizu.ac.jp/conference/ACM/results/A.html )
  @author Yuta Kitamura
  @date 2005-04-09
*/

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// end 17:56

#include <iostream>
#include <vector>
#include <algorithm>

typedef unsigned int uint;

using std::cout;
using std::endl;
using std::cin;
using std::vector;
using std::max_element;

int main()
{
  while (cin) {
    uint members, quorum;
    cin >> members >> quorum;

    if (members == 0 && quorum == 0) break;

    vector<uint> v(100);

    for (uint i = 0; i < members; ++i) {
      uint days;
      cin >> days;

      for (uint j = 0; j < days; ++j) {
	uint day;
	cin >> day;
	++(v[day - 1]);
      }
    }

    vector<uint>::iterator max_it = max_element(v.begin(), v.end());

    if (*max_it < quorum)
      cout << 0 << endl;
    else
      cout << (max_it - v.begin() + 1) << endl;
  }

  return 0;
}