expanding rods

#include<bits/stdc++.h>
using namespace std;
#define suni ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define endl "\n"
#define mn int main()
#define frac() cout.unsetf(ios::floatfield);cout.precision(6);cout.setf(ios::fixed,ios::floatfield);
typedef long long ll;
mn
{
    suni;
    int t; cin>>t;
    for(int i=1;i<=t;i++){
        double L,n,c;
        cin>>L>>n>>c;
        double L1=(1+(n*c))*L;
        double l=0,r=1e18;
        for(int j=1;j<=100;j++){
            double R=(l+r)/2.0;
            double ans=R*2*asin(L/(2.0*R));
            if(ans>L1) l=R;
            else r=R;
        }
        double R=l;
        double h=R-sqrt((R*R)-(L/2.0)*(L/2.0));
        frac();
        cout<<"Case "<<i<<": "<<h<<endl;
    }
}