#include <cstdio>

class A 
{
public:
	virtual void vf();
};
 
class B : public A
{
public:
	void vf()
	{
		printf("B::vf\n");
	}
};
 
int main() 
{
	A a;
	B b;
	b.vf();
	 
	A* pa= &a;
	A* pb= &b;
	//pa->vf();
	//pb->vf();
	return 0;
}