#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <cassert>
#include <limits>
#include <functional>
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) __typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define all(o) (o).begin(), (o).end()
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset(m,v,sizeof(m))
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
using namespace std;
typedef vector<int> vi; typedef pair<int,int> pii; typedef vector<pair<int,int> > vpii; typedef long long ll;
template<typename T, typename U> inline void amin(T &x, U y) { if(y < x) x = y; }
template<typename T, typename U> inline void amax(T &x, U y) { if(x < y) x = y; }

int main() {
	int K;
	while(cin >> K) {
		const int X = 6;
		vector<pair<double,double> > dp(K + 2);
		dp[K + 1] = make_pair(1., 0.);
		for(int i = K - 1; i >= 0; -- i) {
			double c1 = 0, c0 = 0;
			rer(j, 1, 6) {
				auto p = dp[min(K + 1, i + j)];
				c1 += p.first / 6;
				c0 += (1 + p.second) / 6;
			}
			dp[i] = make_pair(c1, c0);
		}
		//c1 * x + c0 = x
		//x = c0 / (1 - c1)
		double ans = dp[0].second / (1 - dp[0].first);
		printf("%.10f\n", ans);
	}
	return 0;
}