#include <bits/stdc++.h>

#define show(x) cout << #x << " = " << x << endl

using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

template <typename T>
ostream& operator<<(ostream& os, const vector<T>& v)
{
    os << "sz=" << v.size() << "\n[";
    for (const auto& p : v) {
        os << p << ",";
    }
    os << "]\n";
    return os;
}

template <typename S, typename T>
ostream& operator<<(ostream& os, const pair<S, T>& p)
{
    os << "(" << p.first << "," << p.second
       << ")";
    return os;
}


constexpr ll MOD = 1e9 + 7;

template <typename T>
constexpr T INF = numeric_limits<T>::max() / 100;

int main()
{
    int k;
    cin >> k;
    vector<long double> dp(k + 6, 0);
    for (int i = k - 1; i >= 0; i--) {
        dp[i] = (dp[i + 1] + dp[i + 2] + dp[i + 3] + dp[i + 4] + dp[i + 5] + dp[i + 6]) / 6 + 1.0;
    }
    cout << fixed << setprecision(10) << dp[0] << endl;
    return 0;
}