while True:
    try:
        s, t = input().split(" ")
        u = s + t
        u1 = list(u)
        u1[0::2] = sorted(u[0::2])  # 奇数位排序
        u1[1::2] = sorted(u[1::2])  # 偶数位排序
        result = ""  # 存放结果
        legal_char = "0123456789abcdefABCDEF"
        for i in u1:
            temp = i  # 当如果i不是16进制的值的时候,加入到result
            if i in legal_char:
                temp = int(i, 16)  # 16进制转10进制
                temp = bin(temp)[2:].zfill(4)  # 10进制转二进制,如果不满4位,左侧补零
                temp = temp[::-1]  # 二进制颠倒
                temp = hex(int(temp, 2))[2:].upper()  # 2进制再转回16进制
            result += temp  # 算出的结果加入到result中
        print(result)

    except:
        break