use std::io::*;

fn rand() -> u32 {
    static mut X: u32 = 123456789;
    static mut Y: u32 = 362436069;
    static mut Z: u32 = 521288629;
    static mut W: u32 = 88675123;
    unsafe {
        let t = X ^ (X << 11);
        X = Y;
        Y = Z;
        Z = W;
        W = (W ^ (W >> 19)) ^ (t ^ (t >> 8));
        W
    }
}

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 k: u32 = itr.next().unwrap().parse().unwrap();

    let mut ans = 0.0;
    for _ in 0..100000 {
        let mut now = 0u32;
        while now != k {
            now += rand() % 6 + 1;
            if now > k {
                now = 0;
            }
            ans += 1.0;
        }
    }
    println!("{:.10}", ans / 100000.0);
}