import java.util.*;

public class Demo {


    static boolean possibility(HashMap<Integer,
            Integer> m, int length, String s) {

        int countodd = 0;

        for (int i = 0; i < length; i++) {
            if (m.get(s.charAt(i) - '0') % 2 == 1)
                countodd++;
            if (countodd > 1)
                return false;
        }

        return true;
    }


    static void largestPalindrome(String s) {

        int l = s.length();
        HashMap<Integer,
                Integer> m = new HashMap<>();

        for (int i = 0; i < l; i++)
            if (m.containsKey(s.charAt(i) - '0')) {
                m.put(s.charAt(i) - '0',
                        m.get(s.charAt(i) - '0') + 1);
            } else {
                m.put(s.charAt(i) - '0', 1);
            }

        if (possibility(m, l, s) == false) {
            System.out.print("No palindromic number available.");
            return;
        }

        char[] largest = new char[l];

        int front = 0;

        for (int i = 9; i >= 0; i--) {

            if (m.containsKey(i) &&
                    m.get(i) % 2 == 1) {

                largest[l / 2] = (char) (i + 48);

                m.put(i, m.get(i) - 1);

                while (m.get(i) > 0) {
                    largest[front] = (char) (i + 48);
                    largest[l - front - 1] =
                            (char) (i + 48);
                    m.put(i, m.get(i) - 2);
                    front++;
                }
            } else {

                while (m.containsKey(i) &&
                        m.get(i) > 0) {
                    largest[front] = (char) (i + 48);
                    largest[l - front - 1] =
                            (char) (i + 48);

                    m.put(i, m.get(i) - 2);

                    front++;
                }
            }
        }

        for (int i = 0; i < l; i++)
            System.out.print(largest[i]);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String s = scanner.nextLine();
        largestPalindrome(s);
    }

}