#include <bits/stdc++.h>
using namespace std;
void _main();
int main() {
	_main();
	return 0;
}
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using vi = std::vector<int>;
using vvi = std::vector<vi>;
using vl = std::vector<ll>;
using vii = std::vector<pair<int, int> >;
using vvl = std::vector<vl>;
using vll = std::vector<pair<ll , ll> >;
using vd = std::vector<double>;
using vvd = std::vector<vd>;
using vs = std::vector<std::string>;
using vvs = std::vector<vs>;
using vb = std::vector<bool>;
using vvb = std::vector<vb>;
using vc = std::vector<char>;
using vvc = std::vector<vc>;
using pii = std::pair<int, int>;
using pll = std::pair<ll, ll>;
using piil = std::pair<pair<int, int>, ll>;
using mii = std::map<int, int>;
using mll = std::map<ll, ll>;
using pql = std::priority_queue<ll>;
using pqi = std::priority_queue<int>;
using pqiil = std::priority_queue<pair<pair<int, int>, ll> >;
using pqii = std::priority_queue<pair<int, int> >;

#define pb push_back
#define ps push
#define eb emplace_back
#define is insert
#define er erase
#define f first
#define s second
#define lb lower_bound
#define ub upper_bound
#define sf(i) sizeof(i)
#define endl "\n"
#define sz(v) ((int)(v).size())
#define all(v) (v).begin(), (v).end()
#define rep(i, L, R) for(ll i = L;i<=R;i++)
#define pcis precision

template<typename T>
struct infinity {
	static constexpr T max=std::numeric_limits<T>::max();
	static constexpr T min=std::numeric_limits<T>::min();
	static constexpr T value=std::numeric_limits<T>::max()/2;
	static constexpr T mvalue=std::numeric_limits<T>::min()/2;
};
template<typename T>constexpr T INF=infinity<T>::value;
constexpr ll lINF=INF<ll>;
constexpr int iINF = INF<int>;
constexpr ld PI = 3.1415926535897932384626;



map<ll ,ll > is;
ll phi(ll N) {
	if (is[N] != 0)return is[N];
	ll res = N;
	for (long i = 2; i <= sqrt(N); i++) {
		if (N % i == 0) {
			res = res - res / i;
			while (N % i == 0) N /= i;
		}
	}
	if (N > 1) res = res - res / N;
	return is[N] = res;
}


ll gcd(ll a, ll b) {
	if (b==0)return a;
	else return gcd(b, a%b);
}

map<ll, double> DP;
// N일때 기댓값 반환

double GET(ll N) {

	if (N==1)return 0;
	if (DP[N] != 0)return DP[N];
	double kitai = 0;
	for (ll i = 1; i*i<=N; i++) {
		// i가 되는 경우
		if (N%i == 0) {
			kitai += GET(i)*((double)phi(N/i));
			if (i != 1 && i*i != N) {
				kitai += GET(N/i)*((double)phi(i));
			}
		}
	}
	kitai+=N;
	kitai =  (kitai)/((double)N-1);
	return DP[N] = kitai;
}

void _main() {

	ll N;
	cin >> N;

	cout.pcis(15);
	cout << GET(N) << endl;





}