#include <iostream>
#include <string>
using namespace std;

int f(int x, int y)
{
  if (x <= 0) {
     return y;
  }
  return f(x - 1, y + 1) - f(x / 2, y * 2);
}

int main()
{
	cout << "answer: " << f(4, -1);
	return 0;
}