Palindromes 100500#5991

Palindromes 100500

1 second

256 megabytes

Easy

It has been a while since there was a problem about palindromes, so let us fix that. You are given a string $s$ . Find its lexicographically smallest substring of length $L$ that is a palindrome.

Recall that a string $a$ is lexicographically smaller than a string $b$ of the same length if there exists an index $i$ $(1 \leq i \leq ∣ a ∣)$ (1 \leq i \leq |a|) such that: $a_{1} = b_{1}$ a_1 = b_1, $a_{2} = b_{2}$ a_2 = b_2, $\dots$ , $a_{i - 1} = b_{i - 1}$ a_{i-1} = b_{i-1}, and $a_{i} < b_{i}$ a_i < b_i. A palindrome is a string that reads the same from left to right and from right to left.

Input

The first line contains $L$ $(1 \leq L \leq ∣ s ∣)$ (1 \leq L \leq |s|) — the length of the required substring. The second line contains $s$ $(1 \leq ∣ s ∣ \leq 100500)$ (1 \leq |s| \leq 100500), consisting of lowercase Latin letters.

Output

Output the lexicographically smallest substring of $s$ that has length $L$ and is a palindrome. If no such substring exists, output 42.

Examples

Example

3
abacaba

aba

Example

2
abcdef

Example 1