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

int main() {
    int n; cin >> n;
    vector<double> L(n);
    for (int i = 0; i < n; i++) cin >> L[i];
    int_fast64_t k; cin >> k;
    double lower = 0, upper = 1e9+1;
    for (int i = 0; i < 100; i++) {
        double middle = (lower + upper) / 2;
        int_fast64_t cnt = 0;
        for (int j = 0; j < n; j++) cnt += (int_fast64_t)(L[j] / middle);
        if (cnt >= k) lower = middle;
        else upper = middle;
    }
    cout << fixed << setprecision(15) << lower << '\n';
    return 0;
}