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

void main()
{

    double a,b,s;
    scanf("%lf%lf",&a,&b);
    if((a==0)||(b==0)){
        s=0;
        printf("%.3lf",s);
        return;
    }else if(b-1.4142*a>=1e-4){
        s=a*a;
    }else if(b-a/2<=1e-4){
        s=3.1416*b*b;
    }else{
        double alfa=2*acos(a/(2*b));
        double s1=b*b*alfa/2-b*b*sin(alfa)/2;
        s=3.1416*b*b-4*s1;
    }
    printf("%.3lf\n",s);
}

I think there is something error in the math.h of this problem.
So I had to use integral to do it.
:(

Can you use Dephi???????????
Or Pascal......
It's more easy to slove this problem.

ok,i havent seen your prog clearly