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

You are given a string of length n. If all of its substrings (not necessarily distinct) 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 substring in lexicographical order.

# Constraints

- 1 \le n \le 10^5
- 1 \le k \le \frac{n(n+1)}{2}

# Example

Input:

baabaa 10

Output:

ab

Explanation: The 10 smallest substrings in order are a, a, a, a, aa, aa, aab, aaba, aabaa, and ab.