#include <bits/stdc++.h>
using namespace std;

int main() {
    int N, L[200020];
    long long K;
    cin >> N;
    for (int i = 0; i < N; i++) {
        cin >> L[i];
    }
    cin >> K;

    auto check = [&](long double l) {
        long long cnt = 0;
        for (int i = 0; i < N; i++) {
            cnt += (int)(L[i] / l);
        }
        return cnt >= K;
    };

    const long double eps = 1e-10;
    long double ok = 0;
    long double ng = 10000000001;
    while (abs(ok - ng) > eps) {
        long double mid = (ok + ng) / 2;
        if (check(mid)) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    cout << fixed << setprecision(10) << ok << endl;
}