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

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

	static void solve(String s) throws Exception {
		String ans = maxValue(s);
		System.out.println(ans);
	}

	static String maxValue(String s) throws Exception {
		char [] arr = s.toCharArray();
		Arrays.sort(arr);
		StringBuilder sb = new StringBuilder();
		for(int i = s.length()-1; i >= 0; i--) {
			sb.append(arr[i]);
		}
		return sb.toString();
	}
}