import java.util.Scanner;
import java.util.Arrays;

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

		char[] c = n.toCharArray();

		Arrays.sort(c);

		for(int i=c.length-1; i>=0; i--) {
			System.out.print(c[i]);
		}
		System.out.println();
	}
}