use proconio::{fastout, input};

#[fastout]
fn main() {
    input! {
        n: u32,
        k: u32,
    }

    println!("{}", output(solve(n, k)))
}

fn solve(n: u32, _k: u32) -> u32 {
    n
}

fn output(ans: u32) -> String {
    (ans / 2).to_string()
        + match ans % 2 {
            0 => ".0",
            1 => ".5",
            _ => unreachable!(),
        }
}