#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>
#include <numeric>

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

constexpr long long MAX = 5100000;
constexpr long long INF = 1LL << 60;
constexpr int inf = 1 << 28;
constexpr long long mod = 1000000007LL;
//constexpr long long mod = 998244353LL;

using namespace std;
typedef unsigned long long ull;
typedef long long ll;


int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/
	int kkt; 
	kkt = 1;
	while (kkt--) {
		ll n; scanf("%lld", &n);
		if (n <= 200) {
			vector<long double> a(n + 6), b(n + 6);
			for (int i = n + 1; i <= n + 5; i++) {
				a[i] = 1;
			}
			for (int i = n - 1; i >= 0; i--) {
				for (int j = 1; j <= 6; j++) {
					a[i] += a[i + j] / 6.0;
					b[i] += b[i + j] / 6.0;
				}
				b[i] += 1;
			}
			long double res = b[0] / (1 - a[0]);
			cout << fixed << setprecision(15) << res << "\n";
		}
		else {
			long double res = n + 5.0 / 3.0;
			cout << fixed << setprecision(15) << res << "\n";
		}
	}

    return 0;
}