#include "iostream"
#include "iomanip"
#include "math.h"
using namespace std;

long double N;
long double ans;
long double num;

int main() {
	cin >> N;
	num = (N + 1)*(N + 1);
	for (int i = 100000; i >= 2; i--) {
		num = num*(N+i)/(num+(N+i)*(N+i))*(N+i);
		ans = (long double)(1)/num;
	//	cout << setprecision(20) << ans << "\n";
	}

	cout << setprecision(20) << ans+0.00001 << "\n";
	return 0;
}