import java.io.BufferedReader; import java.io.Closeable; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.util.Arrays; import java.util.HashSet; import java.util.LinkedList; import java.util.Scanner; import java.util.Set; import java.util.StringTokenizer; public class Main { public static void main(String[] args) throws IOException { Scanner sc = new Scanner(System.in); final int N = sc.nextInt(); long[] input = new long[N]; for(int i = 0; i < N; i++){ input[i] = sc.nextLong(); } final long K = sc.nextLong(); final double EPS = 1e-9; double upper = Arrays.stream(input).max().getAsLong(); double lower = (double)(Arrays.stream(input).min().getAsLong()) / K; while(upper - EPS > lower){ final double middle = upper / 2 + lower / 2; //System.out.printf("%.12f %.12f %.12f \n", upper, lower, middle); long count = 0; for(int i = 0; i < N; i++){ count += input[i] / middle; } if(count >= K){ lower = middle; }else{ upper = middle; } } System.out.printf("%.12f\n", lower); } public static class Scanner implements Closeable { private BufferedReader br; private StringTokenizer tok; public Scanner(InputStream is) throws IOException { br = new BufferedReader(new InputStreamReader(is)); } private void getLine() throws IOException { while (!hasNext()) { tok = new StringTokenizer(br.readLine()); } } private boolean hasNext() { return tok != null && tok.hasMoreTokens(); } public String next() throws IOException { getLine(); return tok.nextToken(); } public int nextInt() throws IOException { return Integer.parseInt(next()); } public long nextLong() throws IOException { return Long.parseLong(next()); } public void close() throws IOException { br.close(); } } }