#include<iostream>
using namespace std;
class Base{
  private:
    int x;
  public:
    virtual void mf1()=0;
    //virtual void mf2(int);
    virtual void mf2();
    void mf3();
    void mf3(double);  
};
void Base::mf2()
{
    cout<<"Base"<<endl;
};
class Derived: private Base
{
  public:
    using Base::mf1;
    using Base::mf2;
    void mf1();
    void mf3();
    void mf4();
};
void Derived::mf1()
{
  cout<<"Derived"<<endl;
  mf2();
};
int main()
{
   Derived a;
   a.mf1();
   a.mf2();
   return 0;
}