#include <iostream>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
using namespace std;

typedef long long ll;

const double kEPS = 1e-10;

int N;
ll K;
vector<int> L;

bool C(double x) {
    ll num = 0;
    for (int i = 0; i < N; i++) {
        num += floor((double)L[i] / x + kEPS);
        if (num >= K) return true;
    }
    return false;
}

void Solve() {
    double lb = 0.0, ub = 2e20;
    for (int i = 0; i < 100; i++) {
        double mid = (lb + ub) / 2.0;
        if (C(mid)) {
            lb = mid;
        } else {
            ub = mid;
        }
    }
    cout << fixed << setprecision(20) << lb << endl;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    cin >> N;
    L = vector<int>(N);
    for (int i = 0; i < N; i++) {
        cin >> L[i];
    }
    cin >> K;

    Solve();

    return 0;
}