#include <iostream>
#include <cmath>
#define pr(s) std::cout << s << std::endl
#define rep(n) for (int i=0;i<(n);i++)
using namespace std;
int main() {
	int k;
	cin >> k;
	if (k <= 6) {
		cout << 1 << endl;
		return 0;
	}
	double sum = 0;
	double* dp = new double[k+5];
	for (int i = 0; i < 5; ++i) {
		dp[k + i] = 0;
	}
	for (int i = 1; i <= k; ++i, sum = 0) {
		for (int j = 1; j <= 6; ++j) {
			sum += dp[k - i + j] / 6;
		}
		dp[k - i] = 1 + sum;
	}
	cout << dp[0] << endl;
}