#include<bits/stdc++.h>
using namespace std;
#define ll  long long
#define pi acos(-1.0)
int main()
{
    ll t,i;
    double a,a1,a2,b,c,d,e,f,j,l,area;
    scanf("%lld",&t);
    for(i=1;i<=t;i++)
    {
        scanf("%lf %lf %lf",&a,&b,&c);
        a1=(a*c)/b;
        a2=(a+a1)*(c+a1)/(b-a1);
        area=a2+a1;
        if(b-a1>0)printf("Case %lld: %.8lf\n",i,area);
        else
        {
            printf("Case %lld: -1\n",i);
        }
    }

    return 0;
}