n=int(input())
P=[]
i=1
while i*i<=n:
  if n%i==0:
    P+=[i,n//i]
  i+=1
P=sorted(set(P))
q=[0]*(n+1)
for i in range(2,n+1):
  if n%i==0:
    p=[]
    c=[]
    for j in range(len(P)):
      if P[j]<=i:
        if i%P[j]==0:
          p+=[P[j]]
          c+=[i//P[j]]
      else:
        break
    for ii in reversed(range(len(p))):
      for jj in range(ii+1,len(p)):
        if p[jj]%p[ii]==0:
          c[ii]-=c[jj]
    q[i]=(sum(c[ii]*q[p[ii]] for ii in range(len(p)-1))+i)/(i-c[len(p)-1])
print(q[n])