Rearrange to Form a Palindrome

Given a string ( s ), determine if it is possible to rearrange its characters to form a palindrome. A string is a palindrome if it reads the same forwards and backwards.

A necessary and sufficient condition for such a rearrangement is that at most one character appears an odd number of times, i.e., [ \sum_{c} \bigl[f(c) \bmod 2\bigr] \leq 1 ] If it is possible, output one possible palindrome; otherwise, output "NO".

inputFormat

Input is provided via standard input (stdin) as a single line containing the string ( s ). The string is non-empty and may contain letters.

outputFormat

Print to standard output (stdout) one possible palindrome rearrangement of ( s ) if it exists; otherwise, print "NO".## sample

racecar

racecar