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.Map;
import java.util.Scanner;
import java.util.TreeMap;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		int K = sc.nextInt();

		TreeMap<Character, Integer> map = new TreeMap<>();
		TreeMap<String, Integer> ansMap = new TreeMap<>();

		for (int i = 0; i < s.length(); i++) {
			char c = s.charAt(i);
			if (map.containsKey(c)) {
				int cnt = map.get(c);
				map.put(c, cnt+1);
			} else {
				map.put(c, 0);
			}
		}
		for (int i = 0; i < s.length(); i++) {

			char c = s.charAt(i);

			for (int j = 1; j <= K; j++) {
				if (i + j > s.length()) {
					break;
				}
				String can = s.substring(i, i+j);
				if (ansMap.containsKey(can)) {
					int cnt = ansMap.get(can);
					ansMap.put(can, cnt+1);
				} else {
					ansMap.put(can, 0);
				}
			}
		}
		int cnt = 0;
		String ans = "";
		for (Map.Entry<String, Integer> e : ansMap.entrySet()) {
			cnt++;
			if (cnt == K) {
				ans = e.getKey();
				break;
			}
		}
		System.out.println(ans);
	}
}
