#include <bits/stdc++.h> 
using namespace std;
#include <ios>
#include <iomanip>
  
int main() {
  int a;
  cin >>a;
  double count = 0;
  double count2 =0;
  double k=1;
  for(int i=1;i<=a;i++){
    if(a%i==0){
      count += k;
      count2 =count2+1/k;
    }
    k++;
  }
  cout << count/count2;
}