import java.io.*; import java.util.*; public class Main { public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); int n = sc.nextInt(); int[] values = new int[n]; for (int i = 0; i < n; i++) { values[i] = sc.nextInt(); } long k = sc.nextLong(); double left = 0; double right = Integer.MAX_VALUE; for (int i = 0; i < 1000000; i++) { double m = (left + right) / 2; long sum = 0; for (int j = 0; j < n && sum < k; j++) { sum += (long)(values[j] / m); } if (sum < k) { right = m; } else { left = m; } } System.out.println(new java.math.BigDecimal(left).toPlainString()); } } class Scanner { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); StringTokenizer st = new StringTokenizer(""); public Scanner() throws Exception { } public int nextInt() throws Exception { return Integer.parseInt(next()); } public long nextLong() throws Exception { return Long.parseLong(next()); } public double nextDouble() throws Exception { return Double.parseDouble(next()); } public String next() throws Exception { if (!st.hasMoreTokens()) { st = new StringTokenizer(br.readLine()); } return st.nextToken(); } }