Rearrange String to Palindrome

You are given an integer n representing the length of a string s and the string s itself. Your task is to rearrange the characters of s to form a palindrome if it is possible. If multiple palindromic arrangements exist, you may output any one of them. If it is not possible to form a palindrome, output NO.

A palindrome is a string that reads the same backward as forward. Formally, a string s is a palindrome if:

[ s = s^R ]

where \( s^R \) denotes the reverse of \( s \). Remember that a valid palindrome can have at most one character that appears an odd number of times.

inputFormat

The input consists of two lines:

• The first line contains a single integer n, which is the length of the string.
• The second line contains the string s of length n composed of lowercase letters.

outputFormat

If it is possible to rearrange the string into a palindrome, output any valid palindromic string. Otherwise, output NO (without quotes).

4
aabb

abba