#include <iostream>
using namespace std;

class I{
public:
 virtual void play() const = 0;
// virtual void play() const 
// void play() const
// {
//    cout << "I::play" << endl;
//  }
};

class W: public I{
public:
  void play() const {
    cout << "W::play" << endl;
  }
};


int main() {

  I instr; 
//instr.play();

  W flute;
  flute.play();

  I* pflute = &flute;
  pflute->play();
//  pflute->W::play();
 
} ///:~