from collections import defaultdict

def make_divisors(n):
    divisors = []
    i = 1
    while i ** 2 <= n:
        if n % i == 0:
            divisors.append(i)
            if i ** 2 != n:
                divisors.append(n // i)
        i += 1
    divisors.sort()
    return divisors

def f(x):
    if x == 1:
        return 0
    P = (x / (x - 1)) ** 2
    D = make_divisors(x)
    dic = defaultdict(int)

    for d in reversed(D):
        tmp = x // d
        for d2 in reversed(D):
            if d == d2:
                break
            if d2 % d == 0:
                tmp -= dic[d2]
        dic[d] = tmp

    dic[1] = d - sum(dic.values())
    ret = 0
    for d in D[:-1]:
        ret += f(d) / x * dic[d]
    return (ret + 1) * x / (x - 1)

N = int(input())
print(f(N))