//Java版代码
import java.util.Arrays;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        char[] s = sc.next().toCharArray();
        Arrays.sort(s);
        System.out.println(s);
    }
}
#Python版代码
print(''.join(sorted(input())))