#include <iostream>
using namespace std;

int K;

double rec(int x) {
    if (x >= K) return 0.0;
    double res = 1.0;
    for (int i = 1; i <= 6; i++) {
        res += rec(x + i) / 6.0;
    }
    return res;
}

void Solve() {
    cout << rec(0) << endl;
}

int main() {
    cin >> K;

    Solve();

    return 0;
}