#include<bits/stdc++.h>
using namespace std;
int main()
{
    int t;
    cin>>t;
    for(int i=1;i<=t;i++)
    {
        long long int ox,oy,ax,ay,bx,by;
        double angle,ao,bo,ab,s;
        cin>>ox>>oy>>ax>>ay>>bx>>by;
        ao=sqrt(((ox-ax)*(ox-ax))+((oy-ay)*(oy-ay)));
        bo=sqrt(((ox-bx)*(ox-bx))+((oy-by)*(oy-by)));
        ab=sqrt(((ax-bx)*(ax-bx))+((ay-by)*(ay-by)));
        angle=(acos(((ao*ao)+(bo*bo)-(ab*ab))/(2*ao*bo)));
        s=ao*angle;
        printf("Case %d: %.10lf\n",i,s);
    }return 0;
}