#include <iostream>
typedef long long ll;
const int MAXN = 1e7 + 5;
using namespace std;
double f[MAXN];
int N;
int gcd(int a, int b) {
	return b == 0 ? a : gcd(b, a % b);
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> N;
	f[1] = 0;
	for (int i = 2; i <= N; ++i) {
		for (int j = 1; j < i; ++j) {
			f[i] += (f[gcd(i, j)] + 1.0) / (i - 1.0);
		}
		f[i] += 1.0 / (i - 1.0);
	}
	cout << f[N] << endl;
	return 0;
}