from collections import defaultdict
from fractions import Fraction


def divisors(n):
    D = {1, n}
    i = 2
    while i*i <= n:
        if n % i == 0:
            D.add(i)
            D.add(n//i)
        i += 1
    return D


def factors(n):
    D = defaultdict(int)
    i = 2
    while i*i <= n:
        if n % i == 0:
            D[i] += 1
            n //= i
        else:
            i += 1
    if n > 1:
        D[n] += 1
    return D


def euler(n):
    e = n
    F = factors(n)
    for p in F:
        e = e*(p-1)//p
    return e


memo = {1: Fraction(0)}


def expected(n):
    if n in memo:
        return memo[n]
    D = divisors(n)
    e = Fraction(1)
    for d in D:
        if d < n:
            e += Fraction(euler(n//d), n) * expected(d)
    memo[n] = e * Fraction(n, n-1)
    return memo[n]


print(float(expected(int(input()))))