#include <iostream>

#include <cmath>

using namespace std;

​

int main() {

  const double E = 2.718281828;

  cout << log(6.0f) << "\n";

  cout << log(E) << "\n";

  cout << log(2.0) << "\n";

  cout << log(1.0) << "\n";

  cout << log(0.0) << "\n";

  cout << log(-1.0f) << "\n";

  return 0;

}

​