#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using vi = vector<i64>;
using vvi = vector<vi>;

vi ls;

bool ok(double a, i64 k) {
    i64 cnt = 0;
    for (i64 l: ls) {
        cnt += floor(l / a);
    }
    return cnt >= k;
}

int main() {
    // assert(freopen("/Users/xuzijian/yukicoder/input5", "r", stdin));
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    cout.setf(ios::fixed);
    cout.precision(20);
    int n;
    cin >> n;
    ls = vi(n);
    for (int i = 0; i < n; i++) {
        cin >> ls[i];
    }

    i64 k;
    cin >> k;

    double l = 0, r = 1e9 + 1;
    for (int i = 0; i < 100; i++) {
        double m = (l + r) / 2;
        if (ok(m, k)) {
            l = m;
        } else {
            r = m;
        }
    }
    cout << l << endl;
}