#include <iostream>
using namespace std;

int k;

double e(int x) {
    if (k <= x)
        return 0;
    else
        return e(x+1)/6 + e(x+2)/6 + e(x+3)/6 + e(x+4)/6 + e(x+5)/6 + e(x+6)/6 + 1;
}

int main() {
    cin >> k;
    cout << e(0) << endl;
    return 0;
}