Lovekey

import java.lang.*;
import java.math.*;
import java.util.*;
import java.io.*;
import java.lang.*;
class Main
{
    public static void main(String[] args)
    {
        String a,b,c;
        int i,len1,len2,len3;
        BigInteger d[]=new BigInteger[201];
        BigInteger s1,s2,s3;
        BigInteger ox1=new BigInteger("0");
        BigInteger ox2=new BigInteger("26");
        Scanner cin=new Scanner(System.in);
        d[0]=BigInteger.valueOf(1);
        for(i=1;i<200;i++)
        {
            d[i]=d[i-1].multiply(BigInteger.valueOf(26));
        }
        while(cin.hasNext())
        {
            a=cin.next();
            b=cin.next();
            len1=a.length();
            len2=b.length();
            s1=BigInteger.valueOf(0);
            s2=BigInteger.valueOf(0);
            for(i=len1-1;i>=0;i--)
            {
                s1=s1.add(BigInteger.valueOf(a.charAt(i)-'A').multiply(d[len1-i-1]));
            }
            for(i=len2-1;i>=0;i--)
            {
                s2=s2.add(BigInteger.valueOf(b.charAt(i)-'A').multiply(d[len2-i-1]));
            }
            s3=s1.add(s2);
            c="";
            while(s3.compareTo(ox1)>0)
            {
                c=c.concat(String.valueOf((char)(s3.mod(ox2).intValue()+'A')));
                s3=s3.divide(ox2);
            }
            len3=c.length();
            for(i=len3-1;i>=0;i--)
            {
                System.out.print(c.charAt(i));
            }
            System.out.println();
        }
    }
}