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

int calculate_circle(double radius);

int main(int argc, char *argv[]) 
{
    printf("%d\n", argc);
    printf("%s\n", argv[argc - 1]);
}

int calculate_circle(float radius) 
{
    int result;
    if (radius < 0) 
    {
      printf("Error: negative radius given for circle calculation.\n");
    }

    result = pow(radius, 2) * M_PI;

    return result;
}