#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream> 
#include<map>
#include <iomanip>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
using namespace std;
#define MAX_MOD 1000000007
#define REP(i,n) for(long long i = 0;i < n;++i)
#define LONG_INF 100000000000000
double dp[100] = {};
double math[100] = {};
int main() {
	int  k;
	cin >> k;
	for (int i = 1;i <= k;++i) {
		for (int q = 1;q <= min(i, 6);++q) {
			dp[i] += dp[i - q] / 6;
		}
		dp[i] += 1;
	}
	cout << dp[k] << endl;
	return 0;
}