import sys, time, random
from collections import deque, Counter, defaultdict
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 61 - 1
mod = 998244353

n = ii()
def solve(x):
    if x == 1:
        return 0
    xi = 1 / x
    ans = 1
    for i in range(2, x + 1):
        if i * i > x:
            break
        if x % i == 0:
            ans += xi * solve(x // i)
            if x // i != i:
                ans += xi * solve(i)
    return ans * x / (x - 1)

print(solve(n))