#include <bits/stdc++.h>
using namespace std;

int main() {
    int K;
    cin >> K;

    double dp[210] = {}, prob[210] = {};
    prob[0] = 1;
    double ret = 0;
    for (int i = 0; i < K; i++) {
        for (int j = 1; j <= 6; j++) {
            if (i + j <= K) {
                dp[i + j] += (dp[i] + prob[i]) / 6;
                prob[i + j] += prob[i] / 6;
            } else {
                ret += (dp[i] + prob[i]) / 6;
            }
        }
    }
    ret /= 1 - prob[K];

    cout << dp[K] / prob[K] + ret * (1 - prob[K]) / prob[K] << endl;
}