import java.util.Arrays;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
String s = sc.next();
char[] arr = s.toCharArray();
Arrays.sort(arr);
for(int i=arr.length-1; i>=0; i--) {
System.out.print(arr[i]);
}
}
}