题解 | #字符串合并处理#

import re
str1, str2 = list(input().split())

str_all = list(str1 + str2)
str_all[::2] = sorted(str_all[::2]) #奇数位排序
str_all[1::2] = sorted(str_all[1::2]) #偶数位排序

result = ""
for n in str_all:
    if re.search(r'[0-9A-Fa-f]', n): # 如果字符在特殊字符范围内
        n = bin(int(n, 16))[2:].rjust(4, '0')[::-1] #十六进制转二进制，去掉前两位，倒序
        n = hex(int(n, 2))[2:].upper() #二进制转十六进制，去掉前两位，大写
    result += n
print(result)