#include <iostream>
using namespace std;
class Mammal {
    public:
        Mammal() {
            cout<<"Mammal constructor\n";
        }
        virtual ~Mammal () {
            cout<<"Mammal destructor\n";
        } 
        virtual void speak() const {
        cout<<"Mammal speak!\n";
        }
};

class Dog: public Mammal {
public:
    Dog() {
        cout<<"Dog constructor\n";
    }
    ~Dog() {
        cout<<"Dog destructor\n";
    }
    void speak() const {
    cout<<"wang wang\n";
    }
};

int main() {
    Mammal*pDog=new Dog ;
    pDog->speak();
    delete pDog;
    return 0;
}