#pragma GCC optimize("Ofast")

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, s, t) for (ll i = s; i < (ll)(t); i++)

template<typename T>
bool chmin(T &x, T y) { return x > y ? (x = y, true) : false; }
template<typename T>
bool chmax(T &x, T y) { return x < y ? (x = y, true) : false; }

struct io_setup {
	io_setup() {
		ios::sync_with_stdio(false);
		std::cin.tie(nullptr);
		cout << fixed << setprecision(15);
	}
} io_setup;

vector<double> mm(1e7+1);
double dfs(int x){
	if(x==1) return 0;
	if(mm[x]!=0) return mm[x];
	double res=x;
	for(int i=1;i<x;i++){
		res+=dfs(gcd(x,i));
	}
	res/=x-1;
	return mm[x]=res;
}

int main(){
	int n;
	cin>>n;	
	cout<<dfs(n)<<"\n";
}