#include <iostream>

class B {};

class A {
public:
    B* b;
    A(B *b = new B()) : b(b) {}
};


int main() {
    A *a1 = new A();
    A *a2 = new A();
    std::cout << a1->b << std::endl;
    std::cout << a2->b << std::endl;
    return 0;
}