#include<iostream>
#include<vector>
#include<iomanip>
#include<cassert>
using namespace std;
int N;
vector<int>D;
long double memo[555];
long double solve(int id)
{
	if(id==0)return 0;
	if(memo[id])return memo[id];
	int N=D[id];
	vector<int>TO(id+1);
	for(int j=0;j<=id;j++)if(N%D[j]==0)TO[j]=N/D[j];
	long double ans=N;
	for(int j=id;j--;)if(N%D[j]==0)
	{
		for(int k=j+1;k<=id;k++)if(D[k]%D[j]==0)TO[j]-=TO[k];
		ans+=solve(j)*TO[j];
	}
	return memo[id]=ans/(N-1);
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cin>>N;
	for(int i=1;i<=N;i++)if(N%i==0)D.push_back(i);
	cout<<fixed<<setprecision(16)<<solve(D.size()-1)<<endl;
}