import java.io.*;
import java.util.*;
import java.math.*;

class Main256 {
	
	public static void out (Object out) {
		System.out.println(out);
	}
	
	public static void main (String[] args) throws IOException {
		BufferedReader br = 
			new BufferedReader(new InputStreamReader(System.in));
		
		char[] c = br.readLine().toCharArray();
		
		Arrays.sort(c);
		for (int i = 0; i < c.length; i++) {
			System.out.print(c[c.length - i - 1]);
		}
		System.out.println();
		
	}
}