#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <fstream>
#include <sstream>
#include<set>
#include<stack>
#include<time.h>
#include <sys/types.h>
#include <tuple>
#include <numeric>
#include <iterator>

typedef long long int ll;
//#include<bits/stdc++.h>


using namespace std;

ll gcd(ll a, ll b) {
    if (a < b)swap(a, b);
    if (b == 0)return a;
    return gcd(b, a % b);
}
int lcm(int a, int b) {
    return a * b / gcd(a, b);
}







int main()
{

    int Q;
    Q = 1;
    //cin >> Q;   

    while (Q--) {
        double k;
        cin >> k;
        vector<double > p(k + 10);
        
        for (int i = 7; i < k+7; i++) {
            for (int j = 1; j <= 6; j++) {
                p[i] += (1 + p[i - j]) / 6;
            }
           // cout << p[i];
        }
        cout << setprecision(20);
        cout << p[k + 6];


    }
    return 0;
}