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

**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 $k$th 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.