#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <iomanip>
using namespace std;
#define INF 1e9
#define PI acos(-1)
typedef long long ll;

double dp[50] = {0};

int main() {
	int k; cin >> k;
	k--;
	
	for (int i = k; i >= 0; i--) {
		dp[i]++;
		for (int j = 1; j <= 6; j++) {
			if (i - j >= 0) {
				dp[i - j] += dp[i]/6.0;
			}
		}
	}

	cout << dp[0] << endl;
	return 0;
}