#define _USE_MATH_DEFINES
#include<stdio.h>
#include<string>
#include<iostream>
#include<cctype>
#include<cstdio>
#include<vector>
#include<stack>
#include<queue>
#include <algorithm>
#include<math.h>
#include<set>
#include<map>
#include<iomanip>

//#include<bits/stdc++.h>



using namespace std;


int main() {

	int t;
	cin >> t;
	double r[40] = {};
	while (t--) {
		r[t] = 1 + (r[t + 1] + r[t + 2] + r[t + 3] + r[t + 4] + r[t + 5] + r[t + 6]) / 6 ;
	}
	cout << r[0] << endl;

	return 0;


}