import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		double[] rates = new double[7];
		rates[1] = 1;
		for (int i = 2; i <= n; i++) {
		    for (int j = 6; j >= 1; j--) {
		        rates[j] = rates[j] * j / 6 + rates[j - 1] * (6 - j + 1) / 6;
		    }
		}
		System.out.println(rates[6]);
	}
}