#include <iostream>

using namespace std;

​

class Animal {

  public:

    virtual void sound() {

      cout << "Animal sound\n";

    }

};

​

class Dog : public Animal {

  public:

    void sound() override {

      cout << "Dog barks\n";

    }

};

​

int main() {

  Animal* a;

  Dog d;

  a = &d;

  a->sound(); // Outputs: Dog barks

  return 0;

}

​