#include <iostream>
#include <math.h>
using namespace std;
double a, b, c, l, R, r;
double tarea;
int main()
{
int num = 0;
while(scanf("%lf %lf %lf %lf", &a, &b, &c, &l) ,a+b+c+l )
{
num ++;
double ll = ( a + b + c ) / 2;
tarea = sqrt( ll * ( ll - a ) * ( ll - b ) * ( ll - c ) );
R = 2 * tarea / (a + b + c) ;
if ( l >= a + b + c ) printf("Case %d: %.2lf\n", num, tarea);
else if( l <= 2 * M_PI * R )
{
printf("Case %d: %.2lf\n", num, l * l / (4 * M_PI) );
}
else
{
r = (a + b + c - l) / ((a + b + c) / R - 2 * M_PI);
double ans = tarea + M_PI * r * r - (r * r * tarea / (R * R));
printf("Case %d: %.2lf\n", num, ans);
}
}
}