human
A string is called palindrome if it reads the same from left to right and from right to left. For example "kazak", "oo", "r" and "mikhailrubinchikkihcniburliahkim" are palindroms, but strings "abb" and "ij" are not.

You are given string s consisting of lowercase Latin letters. At once you can choose any position in the string and change letter in that position to any other lowercase letter. So after each changing the length of the string doesn't change. At first you can change some letters in s. Then you can permute the order of letters as you want. Permutation doesn't count as changes. 

You should obtain palindrome with the minimal number of changes. If there are several ways to do that you should get the lexicographically (alphabetically) smallest palindrome. So firstly you should minimize the number of changes and then minimize the palindrome lexicographically.

Input

The only line contains string s (1 ≤ |s| ≤ 2·105) consisting of only lowercase Latin letters.

Output

Print the lexicographically smallest palindrome that can be obtained with the minimal number of changes.

Examples

Input

aabc

Output

abba

Input

aabcd

Output

abcba

=====
Can you provide a Python code to print the lexicographically smallest palindrome that can be obtained with the minimal number of changes?
assistant
#Here is Python code to print the lexicographically smallest palindrome that can be obtained with the minimal number of changes.

#!/usr/bin/env python3
# 600C_palindrom.py - Codeforces.com/problemset/problem/600/C by Sergey 2015

import unittest
import sys

###############################################################################
# Palindrom Class (Main Program)
###############################################################################

class Palindrom:
    """ Palindrom representation """

    def __init__(self, test_inputs=None):
        """ Default constructor """

        it = iter(test_inputs.split("\n")) if test_inputs else None

        def uinput():
            return next(it) if it else sys.stdin.readline().rstrip()

        # Reading single elements
        self.s = uinput()

        self.cnt = {}
        for c in self.s:
            self.cnt[c] = self.cnt.get(c, 0) + 1

        self.odd = len(self.s) % 2

        self.pcnt = dict(self.cnt)
        for i in reversed(sorted(self.pcnt)):
            if self.pcnt[i] % 2:
                self.pcnt[i] -= 1
                found = 0
                for j in sorted(self.pcnt):
                    if self.pcnt[j] % 2:
                        self.pcnt[j] += 1
                        found = 1
                        break
                if not found:
                    self.pcnt[i] += 1

    def calculate(self):
        """ Main calcualtion function of the class """

        result = []
        mid = []

        for c in sorted(self.pcnt):
            n = self.pcnt[c]
            if n > 0:
                for j in range(n // 2):
                    result.append(c)
                if n % 2:
                    mid.append(c)

        return "".join(result + mid + list(reversed(result)))

###############################################################################
# Unit Tests
###############################################################################

class unitTests(unittest.TestCase):

    def test_single_test(self):
        """ Palindrom class testing """

        # Constructor test
        test = "aabc"
        d = Palindrom(test)
       ...