#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void fallback_print_usage() {
  printf("Usage: ./sqrt number\n");
  printf("Example: ./sqrt 2\n");
  exit(0);
}

void print_sqrt(double number) {
    printf("%.8lf\n", sqrt(number));
}

int main(int argc, char *argv[])
{
    if (argc != 2) {
        fallback_print_usage();
    }
    print_sqrt(atof(argv[1]));
    return 0;
}