#include <stdio.h>
#include <math.h>
int main() {
const double E = 2.718281828;
printf("%f\n", log(6.0));
printf("%f\n", log(E));
printf("%f\n", log(2.0));
printf("%f\n", log(1.0));
printf("%f\n", log(0.0));
printf("%f\n", log(-1.0));
return 0;
}