Lexicographically Smallest Palindrome

Given a string s consisting only of lowercase English letters, you are required to rearrange the characters to form a palindrome. Among all possible palindromes, output the lexicographically smallest one. If it is impossible to form any palindrome from s, output IMPOSSIBLE.

A palindrome is a string that reads the same forwards and backwards. The lexicographical order is defined based on the usual alphabetical order.

Note: The input will be provided to your program via standard input (stdin) and the expected output should be printed to standard output (stdout).

Examples:

• For s = "aabb", one possible palindrome is "abba".
• For s = "abc", no palindrome can be formed, so the output is "IMPOSSIBLE".
• For s = "aaabbbb", the output should be "abbabba".

inputFormat

The input consists of a single line containing a string s of lowercase English letters.

For example:

aabb

outputFormat

Output the lexicographically smallest palindrome that can be formed by rearranging the letters of s, or print IMPOSSIBLE if no palindrome can be formed.

For example:

abba

## sample

aabb

abba

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