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: usize = itr.next().unwrap().parse().unwrap();
    let mut dp: Vec<f64> = vec![0.0; n + 10];

    dp[1] = 1.0;
    for i in 2..n + 1 {
        dp[i] = (dp[i - 1] + 1.0) / 6.0;
        if i > 1 {
            dp[i] += (dp[i - 2] + 1.0) / 6.0;
        } else {
            dp[i] += 1.0 / 6.0;
        }
        if i > 2 {
            dp[i] += (dp[i - 3] + 1.0) / 6.0;
        } else {
            dp[i] += 1.0 / 6.0;
        }
        if i > 3 {
            dp[i] += (dp[i - 4] + 1.0) / 6.0;
        } else {
            dp[i] += 1.0 / 6.0;
        }
        if i > 4 {
            dp[i] += (dp[i - 5] + 1.0) / 6.0;
        } else {
            dp[i] += 1.0 / 6.0;
        }
        if i > 5 {
            dp[i] += (dp[i - 6] + 1.0) / 6.0;
        } else {
            dp[i] += 1.0 / 6.0;
        }
    }

    println!("{:.10}", dp[n]);
}