#include <iostream>
#include <stdio.h>
#include <vector>
#include <map>
#include <stack>
#include <cstring>
#include <utility>
#include <iostream>
#include <iomanip>
#include <list>
#include <queue>
#include <algorithm>
#include <cmath>
#include <unordered_set>
#include <bitset>
#define FOR(i,a,b) for (ll i=(a);i<(ll)(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
#define SUM(v) accumulate(ALL(v),0ll)
#define CL(v) cout<<v<<endl
using ll = long long;
const ll INF=10000000000000;
using namespace std;
int main()
{
	ll n;
	cin>>n;
	double a=0;
	double b=0;
	REP(i,n+1)
	{
		if(i==0)continue;
		if(n%i==0)
		{
				a+=i;
				b+=(double)1/i;
		}	
	}
//	b=1/a;
//	cout<<a<<" "<<b<<endl;
	cout<<a/b<<endl;
    return 0;
}