#include <bits/stdc++.h>

#define show(x) cerr << #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()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    vector<vector<long double>> dp(N, vector<long double>(6, 0));
    dp[0][0] = 1;
    for (ll i = 0; i < N - 1; i++) {
        dp[i + 1][5] = dp[i][5];
        for (ll j = 0; j < 5; j++) {
            dp[i + 1][j] += dp[i][j] * (long double)(j + 1) / 6;
            dp[i + 1][j + 1] += dp[i][j] * (long double)(5 - j) / 6;
        }
    }
    cout << fixed << setprecision(10) << dp[N - 1][5] << endl;

    return 0;
}