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
s = raw_input()
chrindex = []
for i in range(0, 26):
	chrindex.append([])
for i in range(0, len(s)):
	chrindex[ord(s[i])-97].append(i)
K = int(raw_input())
sublist = []
for i in range(0, K):
	sublist.append('')
for i in range(0, 26):
	for j in range(0, len(chrindex[i])):
		word = ''
		for k in range(chrindex[i][j], len(s)):
			word = word + s[k]
			if sublist[-1] < word and sublist[-1] != '': break
			if word not in sublist:
				for p in range(0, K):
					if word < sublist[p]:
						for q in range(0, K-p-1):
							sublist[-1-q] = sublist[-2-q]
						sublist[p] = word
						break
					if sublist[p] == '':
						sublist[p] = word
						break
	if '' not in sublist: break
print sublist[-1]