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

int main(void) {
	cout << fixed << setprecision(15);
	
	int K;
	cin >> K;
	
	vector<double> d(K + 1, 0);
	for(int i = 1; i <= K; ++i) {
		d[i] = 1;
		for(int j = i - 6; j < i; ++j) d[i] += d[j] / 6;
	}
	
	cout << d[K] << "\n";
	
	return 0;
}