#include <iostream>

#include <cmath>

using namespace std;

​

int main() {

  cout << atan2(0.5, 0.5) << "\n";

  cout << atan2(-0.5, -0.5) << "\n";

  cout << atan2(5, 5) << "\n";

  cout << atan2(10, 20) << "\n";

  cout << atan2(5, -5) << "\n";

  cout << atan2(-10, 10) << "\n";

  return 0;

}

​