from sys import stdin,setrecursionlimit#,set_int_max_str_digits
#import pypyjit
#pypyjit.set_param('max_unroll_recursion=-1')
# setrecursionlimit(2000000) # これこどふぉだと無理
# set_int_max_str_digits(200010)
mod = 998244353 
ii = lambda :int(stdin.readline())
mi = lambda :map(int,stdin.readline().split())
li = lambda :list(mi())
gmi = lambda :map(lambda x: int(x) - 1, stdin.readline().split())
gi = lambda :list(map(lambda x: 0 if x == "." else 1,input())) # グリッド入力受け取り
py = lambda :print("Yes")
pn = lambda :print("No")
pf = lambda :print("First") 
ps = lambda :print("Second")
pyn = lambda x: print("Yes") if x else print("No")
vec = [(1,0),(-1,0),(0,-1),(0,1)]
vec1 = [(1,0),(1,1),(0,1),(-1,1),(-1,0),(-1,-1),(0,-1),(1,-1)] #8方向
vec2 = [(1,1),(1,0),(0,-1),(-1,-1),(-1,0),(0,1)] # 六角形グリッド
inf = 10**18
from collections import defaultdict,deque
from heapq import heappop,heappush
#from random import randint

def f(n):
    ret = []
    for i in range(1,int(n**0.5)+1):
        if n % i == 0:
            ret.append(i)
            if i*i != n:
                ret.append(n//i)
    return sorted(ret)

n = ii()
a = f(n) 

dp = defaultdict(float)
dp[1] = 0.0

for x in a[1:]:
    tmp = f(x)[::-1]
    m = len(tmp) 
    cnt = [0]*m 
    for i in range(m):
        c = n//tmp[i]
        cnt[i] += c 
        for j in range(i):
            if tmp[j] % tmp[i] == 0:
                cnt[i] -= cnt[j] 
        if tmp[i] != x:
            dp[x] += dp[tmp[i]]*cnt[i]/(n-cnt[0])
        else:
            dp[x] += n/(n-cnt[i])
    

print(dp[n])