#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <cstdio>
#include <ctime>
#include <assert.h>
#include <chrono>
#include <random>
#include <numeric>
#include <set>
using namespace std;
typedef long long int ll;
typedef unsigned long long ull;

double dp[35];

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int n; cin >> n;
    while(n--)dp[n]=(dp[n+1]+dp[n+2]+dp[n+3]+dp[n+4]+dp[n+5]+dp[n+6])/6.0+1;
    cout << dp[0] << endl;
}