import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;

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