#include <iostream>
#include <vector>
using namespace std;

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

    vector<double> dp(K + 6, 0);
    dp[K] = 0;
    dp[K + 1] = 0;
    dp[K + 2] = 0;
    dp[K + 3] = 0;
    dp[K + 4] = 0;
    dp[K + 5] = 0;
    for (int i = K - 1; i >= 0; --i) {
        dp[i] = (dp[i + 1] + dp[i + 2] + dp[i + 3] + dp[i + 4] + dp[i + 5] + dp[i + 6]) / 6 + 1; 
    }

    cout << dp[0] << endl;
}