#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) for(int i = (n) - 1; (i) >= 0; --i)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD 1000003
#define INF 100000000
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;


int main() {
	int k;
	cin >> k;
	double dp[32] = {};
	REP(i, 32) dp[i]++;
	REP(i, k + 1) {
		FOR(j, 1, 7) {
			dp[i + j] += dp[i] / 6;
		}
	}
	cout << dp[k - 1] << endl;
	return 0;
}