import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        double[][] rates = new double[n][6];
        rates[0][0] = 1;
        for (int j = 1; j < n; j++) {
            for (int i = 5; i > 0; i--) {
                rates[j][i] = rates[j - 1][i] * (i + 1) / 6.0 + rates[j - 1][i - 1] * (6 - i) / 6.0;
            }
            rates[j][0] = rates[j - 1][0] / 6;
        }
        System.out.println(new java.math.BigDecimal(rates[n - 1][5]).toPlainString());
    }
    
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}