두 객체의 값 서로바꾸는것 도와주세요ㅠㅠ

#include <iostream>
#include <utility> // for swap (since C++11)
using namespace std;
 
// Forward declarations
class X;
ostream &operator<<(ostream &, const X&);
 
class X {
public:
	int n;
	ostream &streamOut(ostream &out) const{return (out << n);}
};
 
ostream &operator<<(ostream &out, const X& x){return x.streamOut(out);}
 
void change(X &x, X &y) {
	swap(x, y);
}
 
int main() {
	X a{ 1 };
	X b{ 2 };
 
	change(a, b);
 
	cout << a << ", " << b << endl;
}