#include<bits/stdc++.h>
using namespace std;
double distance(double ax, double ay, double bx, double by)
{
    double a, b, d;
    a = (ax-bx)*(ax-bx);
    b = (ay-by)*(ay-by);
    d = sqrt(a+b);
    return d;
}
int main()
{
    int t;
    cin >> t;
    for(int i = 1; i<=t; i++)
    {
        double ox, oy, ax, ay, bx, by, r, a, s, value, thita;
        cin >> ox >> oy >> ax >> ay >> bx >> by;
        r = distance(ox,oy, ax, ay);
        // cout << r << endl;
        a = distance(ax,ay, bx, by);
        // cout << a << endl;
        value = (2*r*r-a*a)/(2*r*r);
        thita = acos(value);
        //  cout << thita << endl;
        s = r*thita;
        //cout << s << endl;
        printf("Case %d: %.9lf\n",i,s);
    }
    return 0;
}
 

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