## https://yukicoder.me/problems/no/2829

import math

def main():
    N = int(input())

    # 約数の列挙
    sqrt_n = int(math.sqrt(N))
    divisors = []
    for p in range(1, sqrt_n + 1):
        if N % p == 0:
            q = N // p
            divisors.append(p)
            if q != p:
                divisors.append(q)
    divisors.sort(reverse=True)

    # 各divisorたちのgcdとその分布を計算
    divisors.sort()
    gcds = []
    for i in range(len(divisors)):
        d = divisors[i]

        a_map = {}
        for j in reversed(range(i + 1)):
            d_ = divisors[j]

            if d % d_ > 0:
                continue
            
            q = d // d_
            for k in range(j + 1, i + 1):
                if d % divisors[k] == 0:
                    q -= a_map[divisors[k]]
            a_map[d_] = q
        gcds.append(a_map)

    dp = {1:0}
    for i in range(len(divisors)):
        s = divisors[i]
        if s == 1:
            continue

        ans = s
        for key, value in gcds[i].items():
            if key == s:
                continue
            ans += value * dp[key]
        ans /= s - 1
        dp[s] = ans
    
    print(dp[N])



                





    
        















if __name__ == "__main__":
    main()