import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		String N = sc.next();
		
		char[] charN = N.toCharArray();
		
		Arrays.sort(charN);
		
		for(int i = charN.length - 1; i >= 0; i--) {
			System.out.print(charN[i]);
		}
		
		System.out.println();
	}
}