#include <iostream>
using namespace std;

int main(){
	int n;
	cin >> n;
	double dp[n + 1]{};
	for(int i = 1; i <= n; i++){
		for(int j = 1; j <= min(6, i - 1); j++) dp[i] += dp[i - j] / 6;
		dp[i]++;
	}
	cout << dp[n] << endl;
}