fn main() {
    let mut t = String::new();
    std::io::stdin().read_line(&mut t).ok();
    let t: usize = t.trim().parse().unwrap();
    for _ in 0..t {
        let mut r = String::new();
        std::io::stdin().read_line(&mut r).ok();
        let r: f64 = r.trim().parse().unwrap();
        println!("{:.09}", (3 as f64).sqrt() * 3. * r * r / 2. / 2.);
    }
}