#include <iostream>
class base
{
public:
    base() 
    {
        std::cout << "base()";
    }
    virtual ~base() 
    {
        std::cout << "~base()";
    }
    void f()
    {
        std::cout << "base f()";
    }
};
class derived: public base
{
public:
    derived()
    {
        std::cout << "derived()";
    }
    ~derived()
    {
        std::cout << "~derived()";
    }
    void f()
    {
        std::cout << "derived f()";
    }
};
int main()
{
    base* ob = new derived;
    dynamic_cast<derived*>(ob)->f(); 
    return 0;
}