#define _CRT_SECURE_NO_WARNINGS
#define _USE_MATH_DEFINES
#include <iostream>
#include <map>
#include <list>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <algorithm>
#include <utility>
#include <queue>
#include <iomanip>

using namespace std;

double e(int x, int k)
{
	double res = 0;

	if (x >= k) return (0);

	for (int i = 1; i <= 6; i++) {
		res += e(x + i, k) / 6;
	}
	
	return (res + 1);
}

int main(void)
{
	int k;

	cin >> k;

	cout << e(0, k) << endl;

	return (0);
}