import java.util.Scanner; public class Main65 { public static void main(String[] args) { Main65 p = new Main65(); } public Main65() { Scanner sc = new Scanner(System.in); int k = sc.nextInt(); solve(k); } public void solve(int k) { double[] dp = new double[k+1]; for(int i=1;i<dp.length;i++){ for(int j=1;j<=6;j++){ if(i-j<1) break; dp[i] += dp[i-j] / 6.0; } dp[i] += 1; } System.out.println(dp[k]); } }