fn main() {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let h: usize = itr.next().unwrap().parse().unwrap();
    let a: usize = itr.next().unwrap().parse().unwrap();
    let d: usize = itr.next().unwrap().parse().unwrap();

    let mut ans = h as f64;

    for i in 0..=h / a + 1 {
        let mut x = h - i * a;
        let mut y = i as f64;
        if x > 0 {
            let z = (x + d - 1) / d;
            y += z as f64 * 1.5;
        }
        if y < ans {
            ans = y;
        }
    }
    println!("{}", ans);
}