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

public class Main {
    static double[] dp;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        dp = new double[n + 1];
        Arrays.fill(dp, -1);
        dp[0] = 0;
        System.out.println(dfw(n));
    }
    
    static double dfw(int idx) {
        if (dp[idx] >= 0) {
            return dp[idx];
        }
        dp[idx] = 1;
        for (int i = 0; i < idx; i++) {
            dp[idx] += (dfw(i) + dfw(idx - i - 1)) / idx;
        }
        return dp[idx];
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    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 {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}