You are given a string s. Among the different substrings of s, print the K-th lexicographically smallest one.

A substring of s is a string obtained by taking out a non-empty contiguous part in s. For example, if s = `ababc`, `a`, `bab` and `ababc` are substrings of s, while `ac`, `z` and an empty string are not. Also, we say that substrings are different when they are different as strings.

Let X = x_{1}x_{2}...x_{n} and Y = y_{1}y_{2}...y_{m} be two distinct strings. X is lexicographically larger than Y if and only if Y is a prefix of X or x_{j} > y_{j} where j is the smallest integer such that x_{j} \neq y_{j}.

Constraints

* 1 ≤ |s| ≤ 5000
* s consists of lowercase English letters.
* 1 ≤ K ≤ 5
* s has at least K different substrings.

Input

Input is given from Standard Input in the following format:


s
K


Output

Print the K-th lexicographically smallest substring of K.

Examples

Input

aba
4


Output

b


Input

atcoderandatcodeer
5


Output

andat


Input

z
1


Output

z
import java.util.HashSet;
import java.util.PriorityQueue;
import java.util.Scanner;
import java.util.Set;

public class Main implements Runnable {

    private static Scanner sc = new Scanner(System.in);

    public static void main(String[] args) {
        new Thread(null, new Main(), "", 128 * 1024 * 1024).start();
    }

    public void run() {
        String s = sc.next();
        int k = sc.nextInt();
        Set<String> set = new HashSet<>();
        for (int i = 0; i < s.length(); i++) {
            for (int j = 1; j <= k; j++) {
                if (i + j > s.length()) {
                    continue;
                }
                set.add(s.substring(i, i + j));
            }
        }
        PriorityQueue<String> q = new PriorityQueue<>(set);
        for (int i = 0; i < k-1; i++) {
            q.poll();
        }
        System.out.println(q.poll());
    }
}
