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.io.InputStream;
import java.io.PrintStream;
import java.util.LinkedList;
import java.util.List;
import java.util.Scanner;

public class Main {
	InputStream in = System.in;
	PrintStream out = System.out;

	public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		String s = sc.next();
		int K = sc.nextInt();

		List<String> ans = new LinkedList<>();
		for (int i = 0; i < K; i++) {
			ans.add("~" + i);
		}

		NEXTST: for (int st = 0; st < s.length(); st++) {
			NEXTED: for (int ed = st + 1; ed <= s.length(); ed++) {
				String a = s.substring(st, ed);
				for (int i = 0; i < K; i++) {
					int c = a.compareTo(ans.get(i));
					if (c < 0) {
						//小さい
						ans.add(i, a);
						ans.remove(ans.size() - 1);
						continue NEXTED;
					} else if (c > 0) {
						//おおきい
					} else { // c==0
						//次のedを調べる
						continue NEXTED;
					}
				}
				//これ以上このstを調べる必要ない
				continue NEXTST;
			}
		}

		out.println(ans.get(ans.size() - 1));

		sc.close();

	}

	public static void main(String[] args) {
		new Main()._main(args);
	}

}
