#include <iostream>
using namespace std;

class Foo
{
public:
	Foo() = default;
	//Foo() {}
	template<class... T>
	Foo(T&&... args) : a(123)
	{
		cout << "why not enter?" << endl;
	}
	int a;
};
int main() {
	int b = 5;
	Foo f = Foo(1, b);
	return 0;
}