**Time limit:**1.00 s**Memory limit:**512 MB

You are given a string of length n. If all of its distinct substrings are ordered lexicographically, what is the kth smallest of them?

# Input

The first input line has a string of length n that consists of characters a–z.

The second input line has an integer k.

# Output

Print the kth smallest distinct substring in lexicographical order.

# Constraints

- 1 \le n \le 10^5
- 1 \le k \le \frac{n(n+1)}{2}
- It is guaranteed that k does not exceed the number of distinct substrings.

# Example

Input:

babaacbaab 10

Output:

aba

Explanation: The 10 smallest distinct substrings in order are a, aa, aab, aac, aacb, aacba, aacbaa, aacbaab, ab, and aba.