#include <iostream>
using namespace std ;

#include <iostream>
using namespace std;

class student
{
private:
	int id ;
public:
	// constructor
	student(int idP) : id(idP) {}

	// A const function. Cannot change the data
	// members of the class.
	//changes roll with the help of const_cast
	void function1() const
	{
		( const_cast <student*> (this) )->id = 5;
	}

	int getId() { return id; }
};

int main(void)
{
	student s1(3);
	cout << "Old id number: " << s1.getId() << endl;

	s1.function1();

	cout << "New id number: " << s1.getId() << endl;

	return 0;
}