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#include <iostream>
using namespace std;
 
class A{
public:
	A(){};
	~A(){};
	virtual void foo(int a, int b) = 0;
};
class B : public A
{
public:
	B(){};
	~B(){};
	void foo(int a){};
};
 
int main() {
	// your code goes here
	B b;
	b::A::foo();
	return 0;
}

prog.cpp: In function 'int main()':
prog.cpp:20:4: error: cannot declare variable 'b' to be of abstract type 'B'
  B b;
    ^
prog.cpp:10:7: note:   because the following virtual functions are pure within 'B':
 class B : public A
       ^
prog.cpp:8:15: note: 	virtual void A::foo(int, int)
  virtual void foo(int a, int b) = 0;
               ^
prog.cpp:21:2: error: 'b' is not a class, namespace, or enumeration
  b::A::foo();
  ^

Standard output is empty