#include "bits/stdc++.h"

using namespace std;

void solve()
{
	int N;
	cin >> N;
	vector<double> dp(N+1);
	for (int n = N-1; n >= 0; n--)
	{
		int x = min(6, N-n);
		dp[n] = 1;
		for (int i = x; i > 0; i--)
		{
			dp[n] += dp[n+i]/6;
		}
	}

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

int main()
{
	solve();
	//cout << "yui(*-v・)yui" << endl;
	return 0;
}