#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;

int main(){
	int n;
	cin>>n;	
	map<int,double> mp;
	auto dfs=[&](auto self,int x) ->double {
		if(x==1) return 0;
		if(mp.count(x)) return mp[x];
		double res=1;
		for(int i=1;i<x;i++){
			res+=self(self,gcd(i,x))+1;
		}
		res/=x-1;
		return mp[x]=res;
	};
	cout<<dfs(dfs,n)<<endl;
}