#include <iostream>
#define pr(s) std::cout << s << std::endl
#define rep(n) for (int i=0;i<(n);i++)
using namespace std;
int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	int k;
	cin >> k;
	if (k <= 6)cout << 1 << endl;
	double* dp = new double[k];
	double log = 1;
	dp[0] = 0;
	while (abs(log - dp[0]) < 0.0001) {
		double sum = 0;
		for (int i = 1; i <= 6; ++i, sum = 0) {
			for (int j = 1; j < i; ++j) {
				sum += dp[k - i - j] / 6;
			}
			dp[k - i] = 1 + sum + dp[0] / 6;
		}
		for (int i = 7; i <= k; ++i, sum = 0) {
			for (int j = 1; j <= 6; ++j) {
				sum += dp[k - i - j] / 6;
			}
			dp[k - i] = 1 + sum;
		}
		log = dp[0];
	}
	cout << dp[0] << endl;
}