1#include <iostream>
2using namespace std;
3 
4class Animal {
5public:
6    void speak() {
7        cout << "..." << endl;
8    }
9};
10 
11class Dog : public Animal {
12public:
13    void speak() {
14        cout << "Woof!" << endl;
15    }
16};
17 
18int main() {
19    Animal a;
20    Dog d;
21    a.speak();
22    d.speak();
23    Animal* ptr = &d;
24    ptr->speak();
25    return 0;
26}