Geometry

#include <stdio.h>
#include <math.h>
#define pi 3.14
int main()
{
    double x,y;
    scanf("%lf %lf", &x, &y);
    double r = y/4.0;
    double cir_area = pi*r*r;
    double a = x - r;
    double b = r*2.0;
    double c = (a*a) + (b*b);
    double tri_area = (y/4.0) * sqrt((4.0*c) - (y*y));
    if((cir_area+tri_area) >= (x*y)) printf("-1\n");
    else printf("%lf\n", (x*y)- (cir_area+tri_area));
    return 0;
}