#include <iostream>
using namespace std; 

class A { 
public: 
    A() {} 
    ~A() {} 
    void f(){cout<<"A::f();"<<endl;}
}; 
 
class B: virtual public A { 
public: 
    B() {} 
    ~B() {}
    void f(){cout<<"B::f();"<<endl;}
}; 

int main(){
     A * a = new B();
     B * b = dynamic_cast<B *>(a);
     b->f();
     delete a;
}