What will be the output of the following C++ code?

#include <iostream>
#include <string>
using namespace std;
class A
{
	int a;
    public:
	virtual void func() = 0;
};
 
class B: public A
{
    public:
	void func(){
		cout<<"Class B"<<endl;
	}	
};
 
int main(int argc, char const *argv[])
{
	A *a;
	a->func();
	return 0;
}