import java.util.*;
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]);
		}
		System.out.println();
		
		
	}
}