e-Tutor_5

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI 3.1415926
double CircusAreaCalc(double r)
{
    return pow(r, 2) * PI;
}
int main(int argc, const char * argv[])
{
    double AreaSum = 0.0 , Radius = 0.0;
    char input[100];

    while(1)
    {
        scanf("%s",input);
        Radius = atof(input);
        if(Radius == 0)
        {
            printf("%.5f\n",AreaSum);
            return 0;
        }
        AreaSum += CircusAreaCalc(Radius);
    }

    return 0;
}