public class A {
    public:
        int a;
        A():a(2){}
        A(A & aa):A(){ this->a = aa->a; }
};

public class B: public A {
    public:
        B():A(){ a+=3; }
        B(B & b){}
};

void main(){
    B b0;
    B b1(b0);
}