#include <iostream>
#include<set>
#include<vector>
#include<algorithm>
using namespace std;
int t;
int main()
{

    int a[]={15,20,35,30};
    set<int> S1(a,a+4 );

    for(int i=0;i<3;++i)
        cout<<*(S1+i);
   // while(S2!=S1.end()){
     //   cout<<*S2;
       // S2=

   /*vector<int> a;
   a.push_back(15);
   a.push_back(10);
   a.push_back(20);
   a.push_back(19);
   sort(a.begin(),a.begin()+a.size());
    while(a.empty()==0){
      cout<<*a.begin()<<" ";
      a.erase(a.begin());
    }
    */

    return 0;
}