import java.util.*;

/**
 * HJ34 图片整理
 */
public class HJ034 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            String str = sc.nextLine();
            char[] chars = str.toCharArray();
            Arrays.sort(chars);
            StringBuilder resultStr = new StringBuilder();
            for (char aChar : chars) {
                resultStr.append(aChar);
            }
            System.out.println(resultStr);
        }
        sc.close();
    }

}