#include"bits/stdc++.h"

//#include<bits/stdc++.h>
using namespace std;
#define print(x) cout<<x<<endl;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a) for(int i=0;i<a;i++)
typedef long long ll;
const ll mod = 10000000000;

ll n, k;
double l[200002];

bool check(double mid) {
	ll count = 0;
	REP(i, n) {
		count += (int)(l[i] / mid);
	}
	if (count >= k)return 1;
	else { return 0; }
}

int main() {
	cin >> n;
	REP(i, n) { cin >> l[i]; }
	cin >> k;
	double lb =0, ub = mod;
	REP(i,100) {
		double mid = (lb + ub) / 2.0;
		if (check(mid)) { lb = mid; }
		else { ub = mid; }
	}
	printf("%.14f\n", ub);
	return 0;
}