import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;

import static java.lang.System.in;


public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        String N = reader.readLine();
        int[] table = new int[10];
        for (int i = 0; i < N.length(); i++) {
            table[Character.getNumericValue(N.charAt(i))] += 1;
        }
        

        StringBuilder builder = new StringBuilder();
        for (int i = 9; i >= 0; i--) {
            int j = i;
            while (table[j] != 0) {

                builder.append(j);
                table[j] -= 1;
            }
        }

        System.out.println(builder.toString());
    }
}