#include <iostream>

class Foo {
public:
	Foo() {
		std::cout << "ctor" << std::endl;
	}
	
	Foo(Foo& f) {
		std::cout << "copy ctor" << std::endl;
	}
	
	Foo& operator=(Foo& f) {
		std::cout << '=' << std::endl;
	}
};

int main() {
	Foo a;
	Foo b = a;
	
	Foo c;
	Foo d;
	c = d;
	return 0;
}