Given a string, your task is to reorder its letters in such a way that it becomes a palindrome (i.e., it reads the same forwards and backwards).

The only input line has a string of length $n$ consisting of characters A–Z.

Print a palindrome consisting of the characters of the original string. You may print any valid solution. If there are no solutions, print "$\text{NO SOLUTION}$". $$ 1 \leq n \leq 10^6 $$