import java.util.*;

public class Main {
	public static void main (String[] args) {
    	Scanner sc = new Scanner(System.in);
    	int n = sc.nextInt();
    	double[][] dp = new double[7][n];
    	dp[1][0] = 1;
    	for (int i = 1; i < n; i++) {
    	    for (int j = 1; j <= 6; j++) {
    	        dp[j][i] = dp[j][i - 1] * j / 6 + dp[j - 1][i - 1] * (6 - j + 1) / 6; 
    	    }
    	}
    	System.out.println(dp[6][n - 1]);
	}
}