007 返回什么才好呢

#include <iostream>
using namespace std;
class A {
public:
	int val;

	A(int n):val(n) {}
	A():val(123){}
	A & GetObj() {
		return *this;
	}

};
int main()
{
	int m,n;
	A a;
	cout << a.val << endl;
	while(cin >> m >> n) {
		a.GetObj() = m;
		cout << a.val << endl;
		a.GetObj() = A(n);
		cout << a.val<< endl;
	}
	return 0;
}