#include <iostream>
#include <set>

using namespace std ;

class student
{
  public:
   int id ;
   student( int idP )
    {
      id = idP ;
	}

   bool operator  <(const student& obj1 )  const
    {
       return id < obj1.id ;
	}
};


int main()
{
	set< student > set1 ;
    student  obj1(1) ;
    student  obj2(2) ;
    student  obj3(1) ;

    set1.insert(  obj1 ) ;
    set1.insert(  obj2 ) ;
    set1.insert(  obj3 ) ;

    for (student st1 : set1 )
	{
			std::cout << st1.id << ' ';
    }
   std::cout << '\n';



	return 0;
}