#include <iostream>
#include <iomanip>
#include <vector>

using ldouble = long double;

void solve() {
    int k;
    std::cin >> k;

    std::vector<ldouble> dp(k + 1, 1);
    dp[k] = 0;

    for (int d = k - 1; d >= 0; --d) {
        for (int f = 1; f <= 6; ++f) {
            dp[d] += dp[std::min(k, d + f)] / 6;
        }
    }

    std::cout << std::fixed << std::setprecision(10)
              << dp[0] << std::endl;
}

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

    solve();

    return 0;
}