#include <stdio.h>

int main(int argc, char argv[]) {
  int n, m, q, i, j, date, conv[99], conv_max;
  for (;;) {
    scanf("%d", &n), scanf("%d", &q);
    if (n == 0 && q == 0) return 0;
    for (j = 0; j < 99; j++) conv[j] = 0;
    conv_max = 0;
    for (i = 0; i < n; i++) {
      scanf("%d", &m);
      for (j = 0; j < m; j++) {
	scanf("%d", &date);
	conv[date - 1]++;
      }
    }
    date = -1;
    for (j = 0; j < 99; j++) {
      if (conv[j] <= conv_max || conv[j] < q) continue;
      conv_max = conv[j];
      date = j;
    }
    printf("%d\n", date + 1);
  }
}