from collections import defaultdict

def factorize(x):
  ans = []
  i = 2
  while i*i <= x:
    if x % i == 0:
      c = 0
      while x % i == 0:
        x //= i
        c += 1
      ans.append((i,c))
    i += 1
  if x != 1:
    ans.append((x,1))
  return ans


N = int(input())

arr = factorize(N)
#print(arr)
L = len(arr)

tmp = [(1,1)]
for p,e in arr:
  tmp_ = []
  for d,v in tmp:
    tmp_.append((d,v))
    d *= p
    v *= p-1
    for _ in range(e):
      tmp_.append((d,v))
      d *= p
      v *= p
  tmp = tmp_

phi = {d:v for d,v in tmp}
#print(phi)

dp = {}
dp[1] = 0

divsors = list(phi.keys())
divsors.sort()


for d in divsors[1:]:
  dp[d] = d
  for d_ in divsors:
    if d > d_ and d % d_ == 0:
      dp[d] += dp[d_] * phi[d//d_]
  dp[d] /= d-1
  
print(dp[N])