import java.util.*;

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