#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef tuple<int, int> duo;
const int dx[] = {0, 0, 1, -1, 1, 1, -1, -1};
const int dy[] = {1, -1, 0, 0, 1, -1, 1, -1};
const int Mod = 1000000000 + 0;
//{{{ templates
#define TT_ template<typename T>inline
#define TTF_ template<typename T,typename F>inline
TT_ T sq(T x){return x*x;}
TT_ T In(){T x;cin>>x;return x;}
TT_ void Out(T&x){cout<<x;}
TT_ void sort(T&v){sort(begin(v),end(v));}
TT_ void revs(T&v){reverse(begin(v),end(v));}
TT_ void uniq(T&v){sort(v);v.erase(unique(begin(v),end(v)),end(v));}
TT_ int ubnd(T&v,typename T::value_type x){return upper_bound(begin(v),end(v),x)-begin(v);}
TT_ int lbnd(T&v,typename T::value_type x){return lower_bound(begin(v),end(v),x)-begin(v);}
TTF_ void inpt(T&v,int n,F f){for(v.reserve(n);n--;v.emplace_back(f()));}
TTF_ void show(T&v,F f,string d=" ",string e="\n"){int i=0;for(auto&x:v)i++&&(cout<<d),f(x);cout<<e;}
TT_ typename T::iterator minel(T&v){return min_element(begin(v),end(v));}
TT_ typename T::iterator maxel(T&v){return max_element(begin(v),end(v));}

inline void fast_io(){ios_base::sync_with_stdio(0);cin.tie(0);}
inline int in(){int x;scanf("%d",&x);return x;}
inline ll pow_mod(ll a,ll k,ll m){ll r=1;for(;k>0;a=a*a%m,k>>=1)if(k&1)r=r*a%m;return r;}
inline ll mod_inv(ll a,ll p){return pow_mod(a,p-2,p);}
//}}} priority_queue queue deque front stringstream max_element min_element insert count make_tuple

int main()
{
  int N, Q;
  while (N = in(), Q = in(), N || Q){
    int bkt[128] = {};
    for (int i = 0; i < N; i++){
      for (int x = in(); x--;){
        bkt[in()]++;
      }
    }
    int maxi = 0;
    for (int i = 1; i < 128; i++){
      if (bkt[i] >= Q && bkt[maxi] < bkt[i]){
        maxi = i;
      }
    }
    cout << maxi << endl;
  }
  return 0;
}
#include <iostream>
using namespace std;
int main(){
  int N,Q,i,I,M,data,max,result;
  int box[100]={};
  while(1){
  cin>>N>>Q;
  if(N==0||Q==0) break;
  for(i=1;i<=N;i++){
    cin>>M;
    for(I=1;I<=M;I++){
      cin>>data;
      box[data]++;
    }
  }
  max=-1;
  for(i=0;i<100;i++){
    if(max<box[i]){
      max=box[i];
      result=i;
    }
  }
  if(box[result]<Q) cout<<"0"<<endl;
  else cout<<result<<endl;
  for(i=0;i<100;i++){
    box[i]=0;
  }
  }
  return 0;
}