#include <bits/stdc++.h>
using namespace std;

int main() {
	int K;
	cin >> K;
	
	vector<double> P(K + 1, 0), E(K + 1, 0);
	P[0] = 1;
	for(int i = 1; i <= K; ++i) {
		for(int t = 1; t <= 6 and t <= i; ++t) {
			P[i] += P[i - t] / 6;
			E[i] += E[i - t] / 6;
		}
		E[i] += 1;
	}
	
	cout << E[K] / P[K] << "\n";
}