#include <iostream>

class A{
        protected:
                void a1(){
                        std::cout << "apa" << std::endl;
                }
        private:
                void a2(){}
};

class B: public A
{
        public:
        void b(){
                a1();
                //a2(); <- illegal
        }
};

int main()
{
        B b;
        b.b();
        //b.a1(); <- illegal
        //b.a2(); <- illegal
}