import java.util.*;

public class Exercise62{
  public static void main (String[] args){

    Scanner sc = new Scanner(System.in);

    String str = sc.next();

    String[] array = str.split("");

    Arrays.sort(array, Comparator.reverseOrder());

    String sortedStr = String.join("",array);

    System.out.println(sortedStr);
  }
}