#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int N; cin >> N;
	vector<int> L(N);
	for (int i = 0; i < N; i++) cin >> L[i];
	ll K; cin >> K;
	double lb = 0, ub = 1000000000;
	for (int k = 0; k < 500; k++) {
		double mid = (lb + ub) / 2;
		ll cnt = 0;
		for (int i = 0; i < N; i++)
			cnt += floor(L[i] / mid);
		if (cnt >= K) lb = mid;
		else ub = mid;
	}
	printf("%.15f\n", lb);
}