use std::io::*;

fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n:f64 = itr.next().unwrap().parse().unwrap();
    println!("{:.10}", 1.0 / n);
}