import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] arr = new int[n];
        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
        }
        int k = sc.nextInt();
        double left = 0.0000000001;
        double right = 1000000000;
        while (right - left > 0.00000000001) {
            double m = (left + right) / 2;
            int count = 0;
            for (int i = 0; i < n; i++) {
                count += (int)(arr[i] / m);
            }
            if (count < k) {
                right = m;
            } else {
                left = m;
            }
        }
        System.out.println(left);
    }
}