#include <iostream>

using namespace std;


class MyAbstractClass
{
public:
  virtual void Hello()=0;
  void GoodBye()
  {cout<<"MyAbstractClass::GoodBye\n";}
};

class MyDerivedClass : MyAbstractClass
{
public:
  void foo()
  {cout<<"MyDerivedClass::foo()";}
};

int main()
{
  //MyDerivedClass D1;

  return 0;
}