#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace std;
using mint = atcoder::modint998244353;
using ld = long double;
int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    int K;
    cin >> K;
    vector<vector<ld>> A(K + 1, vector<ld>(K + 2));
    for (int i = 0; i < K; i++) {
        A[i][i] = 6;
        for (int j = 1; j <= 6; j++) {
            int k = (i + j > K ? 0 : i + j);
            A[i][k] -= 1;
        }
        A[i][K + 1] = 6;
    }
    A[K][K] = 1;
    int rank = 0;
    for (int j = 0; j < K + 2; j++) {
        for (int i = rank; i < K + 1; i++) {
            if (A[i][j] != 0) {
                if (i != rank) swap(A[i], A[rank]);
                break;
            }
        }
        if (A[rank][j] == 0) continue;
        ld t = A[rank][j];
        for (int it = 0; it < K + 2; it++) A[rank][it] /= t;
        for (int i = 0; i < K + 1; i++) {
            if (i != rank && A[i][j] != 0) {
                ld x = A[i][j];
                for (int it = 0; it < K + 2; it++) A[i][it] -= x * A[rank][it];
            }
        }
        rank++;
        if (rank == K + 1) break;
    }
    cout << fixed << setprecision(16) << A[0][K + 1] << "\n";
}