import java.util.*;

public class Run {
    public static void main (String arg[]) {
        Scanner scan = new Scanner(System.in);
        String ans = "";
        String N = scan.next();
        ArrayList A = new ArrayList();
        for (int i = 0; i < N.length(); i++) A.add(Integer.parseInt(N.substring(i, i+1)));
        Collections.sort(A);
        for (int i = N.length(); i > 0; i--) ans += A.get(i-1);
       System.out.println(ans);
    }
}