#include <iostream>
#include <string>

using std::string;
using std::cout;
using std::endl;

struct A
{
	string & f ()
	{
		static string s;
		cout << &s << endl;
		s += "Hello World";
		return s;
	}
};

int main()
{
	A a1;
	A a2;

	cout << a1.f() << endl;
	cout << a2.f() << endl;
}