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

public class No256 {

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

}