import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
#sys.setrecursionlimit(10**9)
#sys.set_int_max_str_digits(0)
#input = sys.stdin.readline
def make_divisors(n):
    lower_divisors , upper_divisors = [], []
    i = 1
    while i*i <= n:
        if n % i == 0:
            lower_divisors.append(i)
            if i != n // i:
                upper_divisors.append(n//i)
        i += 1
    return lower_divisors + upper_divisors[::-1]
n = int(input())
@functools.lru_cache(maxsize=100000000)
def calc(x):
    if x == 1:
        return 0
    res = 0
    div = make_divisors(x)
    c = collections.defaultdict(int)
    for i in reversed(div):
        if i == x:
            c[x] = 1
            continue
        ans = x//i
        for j in div:
            if j % i == 0:
                ans -= c[j]
        c[i] = ans
        res += ans * calc(i)

    res /= x
    res += 1
    
    return res / (1 - 1/x)
print(calc(n))