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 sai1: Vec<usize> = [2, 3, 5, 7, 11, 13].to_vec();
    let sai2: Vec<usize> = [4, 6, 8, 9, 10, 12].to_vec();
    let mut seki = vec![0.0; 202];
    for i in 0..6 {
        for j in 0..6 {
            seki[sai1[i] * sai2[j]] += 1.0;
        }
    }
    let k: usize = itr.next().unwrap().parse().unwrap();
    println!("{:.15}", seki[k] / 36.0);
}