import java.util.Arrays;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        char[] N = sc.next().toCharArray();

        Arrays.sort(N);

        for (int i = N.length - 1; i >= 0; i--) {
            System.out.print(N[i]);
        }

    }

}