import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String N = sc.next();
    int len = N.length();
    String[] num = new String[len];
    for(int i = 0; i < len; i++) {
      num[i] = String.valueOf(N.charAt(i));
    }
    Arrays.sort(num);
    for(int i = len - 1; i >= 0; i--) {
      System.out.print(num[i]);
    }
  }
}