from fractions import Fraction

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())
yaku = make_divisors(N)
A = sum(yaku)
B = 0
for y in yaku:
    B += Fraction(1, y)
ans = A/B
print(ans)