//通俗易懂
import java.util.*;
import java.io.*;
public class Main{
    public static void main(String[] args) throws IOException{
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        String s=null;
        while((s=br.readLine())!=null){
            String[] s1=s.split(" ");
            String str=s1[0].concat(s1[1]);
            char[] chars1=new char[(int)Math.ceil((double)(str.length()/2.0000))];//奇数的话,存放偶数的数组应该是str.length/2,向上取整
            char[] chars2=new char[str.length()/2];
            char[] chars=str.toCharArray();
            for(int i=0;i<chars.length;i++){
                if(i%2==0) chars1[i/2]=chars[i];
                else if(i%2==1) chars2[i/2]=chars[i];
            }
            Arrays.sort(chars1);
            Arrays.sort(chars2);
            for(int i=0;i<chars.length;i++){
                if(i%2==0) chars[i]=chars1[i/2];
                else if(i%2==1) chars[i]=chars2[i/2];
            }
            //String ss2=String.valueOf(chars);
            //System.out.println(ss2);
            for(int i=0;i<chars.length;i++){
                if(chars[i]=='0') chars[i]='0';
                else if(chars[i]=='1') chars[i]='8';
                else if(chars[i]=='2') chars[i]='4';
                else if(chars[i]=='3') chars[i]='C';
                else if(chars[i]=='4') chars[i]='2';
                else if(chars[i]=='5') chars[i]='A';
                else if(chars[i]=='6') chars[i]='6';
                else if(chars[i]=='7') chars[i]='E';
                else if(chars[i]=='8') chars[i]='1';
                else if(chars[i]=='9') chars[i]='9';
                else if(chars[i]=='a' || chars[i]=='A') chars[i]='5';
                else if(chars[i]=='b' || chars[i]=='B') chars[i]='D';
                else if(chars[i]=='c' || chars[i]=='C') chars[i]='3';
                else if(chars[i]=='d' || chars[i]=='D') chars[i]='B';
                else if(chars[i]=='e' || chars[i]=='E') chars[i]='7';
                else if(chars[i]=='f' || chars[i]=='F') chars[i]='F';
            }
            String ss=String.valueOf(chars);
            System.out.println(ss);
        }
    }
}