#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>
#include <numeric>
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
constexpr long long MAX = 5100000;
constexpr long long INF = 1LL << 60;
constexpr int inf = 1000000007;
constexpr long long mod = 1000000007LL;
//constexpr long long mod = 998244353LL;
const long double PI = acos((long double)(-1));

using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;

struct Edge {
	int to;
	int money;
	int time;
	Edge(int _to, int _money, int _time) :to(_to), money(_money), time(_time) {}
};
vector<int> v[4];
int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/
	using Real = double;
	ll n; scanf("%lld", &n);
	vector<ll> l(n); for (int i = 0; i < n; i++) scanf("%lld", &l[i]);
	ll k; scanf("%lld", &k);
	Real lf = 0;
	Real rg = inf;
	for (int i = 0; i <= 100; i++) {
		Real mid = (lf + rg) / 2.0;
		ll cnt = 0;
		for (int i = 0; i < n; i++) {
			cnt += (ll)(l[i] / mid + 1e-14);
		}
		if (cnt >= k) lf = mid;
		else rg = mid;
	}
	printf("%.12f\n", lf);
	return 0;
}