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());

    str = "";
    for (int i = 0; i < array.length; i++){
      str += array[i];
    }

    System.out.println(str);
  }
}