#include<cstdio>
#include<iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>
#include<limits>

#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()

using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ll, string> pls;

int k;

double dfs(double x) {
	if (x >= k)return 0;
	if (x == k - 1)return 1;
	return x = dfs(x + 1) * 1 / 6 + dfs(x + 2) * 1 / 6 + dfs(x + 3) * 1 / 6 + dfs(x + 4) * 1 / 6
		+ dfs(x + 5) * 1 / 6 + dfs(x + 6) * 1 / 6 + 1;
}

int main()
{
	cin >> k;
	printf("%.10f\n", dfs(0));
	return	0;
}