use std::collections::{BTreeSet, HashMap, HashSet, VecDeque};

use proconio::marker::Chars;

fn main() {
    proconio::input! {
        h: i32,
        a: i32,
        d: i32,
    }
    let max_normal_attack_num = h / a + if h % a == 0 { 0 } else { 1 };
    let m = (0..=max_normal_attack_num)
        .map(|natk| {
            let remain_hp = h - natk * a;
            if remain_hp > 0 {
                natk as f64 + (remain_hp / d + if remain_hp % d == 0 { 0 } else { 1 }) as f64 * 1.5
            } else {
                natk as f64
            }
        })
        .fold(0.0 / 0.0, f64::min);
    println!("{m}");
}