#include <stdio.h>
#include <math.h>
int main() {
printf("%f\n", atan2(0.5, 0.5));
printf("%f\n", atan2(-0.5, -0.5));
printf("%f\n", atan2(5, 5));
printf("%f\n", atan2(10, 20));
printf("%f\n", atan2(5, -5));
printf("%f\n", atan2(-10, 10));
return 0;
}