#include <bits/stdc++.h>

using namespace std;

int main() {
    cout << fixed << setprecision(20);
    int k;
    cin >> k;
    long double p = (long double)1 / (long double)6;
    vector<long double> dp(50 , 0);
    for (int i = k - 1; i >= 0; i--) {
        dp[i] += p * (dp[i + 1] + dp[i + 2] + dp[i + 3] + dp[i + 4] + dp[i + 5] + dp[i + 6]) + 1.0;
    }
    cout << dp[0] << endl;
    return 0;
}