In this problem:
1. Given a string consisting only of digit '1' to '9' and each digit character appears at most once,
2. Reorder the string to form palindromes.
(A palindrome (回文) is a word, phrase, number, or other sequence of characters which reads the same backward or forward.)
3. Among all the possible palindromes, find the one with the smallest integer value.
In palindrom, each digit characters in string must appear twice.
For example, the input string is 321.
And all possible palindroms made by the combination of those three digits are
123321
132231
213312
231132
312213
321123
The smallest value of above numbers is 123321.
The input is a string which consists only of digit characters '1' to '9'.
1 ≤ string length L ≤ 9
The smallest value of palindrome.
Note : You need to print a newline at the end of output