#include "bits/stdc++.h"
#include <unordered_set>

#define _CRT_SECURE_NO_WARNINGS

#define REP(i, n) for(decltype(n) i = 0; i < (n); i++)
#define REP2(i, x, n) for(decltype(x) i = (x); i < (n); i++)

#define ALL(a) (a).begin(),(a).end()
#define SORT(c) sort((c).begin(),(c).end())
#define DESCSORT(c) sort(c.begin(), c.end(), greater<int>())

using namespace std;

const int dy[] = { 0, 1, 0, -1 };
const int dx[] = { 1, 0, -1, 0 };

using LL = long long int;
using LD = long double;

const int INF = (1 << 30) - 1;
const LL INF64 = ((LL)1 << 62) - 1;
const double PI = 3.1415926535897932384626433832795;

using pii = pair<int, int>;
using pll = pair<LL, LL>;
using pdd = pair<double, double>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vl = vector<LL>;
using vvl = vector<vl>;
using vvvl = vector<vvl>;
using vd = vector<double>;
using vvd = vector<vd>;
using vs = vector<string>;
using vb = vector<bool>;
using vvb = vector<vb>;

struct Point {
	double x, y;
};



int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	double k;
	cin >> k;

	vd dp(6);

	int cnt = 0;
	REP2(i, 6, k + 6) {
		double t =
			dp[i - 1] * (1.0 / 6.0) +
			dp[i - 2] * (1.0 / 6.0) +
			dp[i - 3] * (1.0 / 6.0) +
			dp[i - 4] * (1.0 / 6.0) +
			dp[i - 5] * (1.0 / 6.0) +
			dp[i - 6] * (1.0 / 6.0) + 1.0;

		dp.push_back(t);
		cnt++;
	}

	printf("%.10lf\n", dp[5 + cnt]);
	return 0;
}