using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var dp = Enumerable.Repeat(-1.0, n + 1).ToArray();
        WriteLine(DFS(n, dp));
    }
    static double DFS(int a, double[] dp)
    {
        if (dp[a] >= 0) return dp[a];
        if (a == 1)
        {
            dp[a] = 0;
            return dp[a];
        }
        var sum = 0.0;
        for (var i = 1; i < a; ++i)
        {
            sum += DFS(GCD(a, i), dp);
        }
        dp[a] = (sum / a + 1) * a / (a - 1);
        return dp[a];
    }
    static int GCD(int a, int b)
    {
        if (a < b) return GCD(b, a);
        if (a % b == 0) return b;
        return GCD(b, a % b);
    }
}