#include <iostream>

#include <cmath>

using namespace std;

​

int main() {

  cout << log2(64.0) << "\n";

  cout << log2(10.0f) << "\n";

  cout << log2(3.1623) << "\n";

  cout << log2(1.0) << "\n";

  cout << log2(0.0f) << "\n";

  cout << log2(-1.0f) << "\n";

  return 0;

}

​