from pickle import TRUE
import sys
def isOushu(num):
if num%2 ==0:
return True
else:
return False
while True:
try:
str1,str2 =input().split()
#1、合并
s = str1+str2
s = list(s)
#2、排序
n = len(s)
s1,s2 =[],[]
l1,l2 =[],[]
ns =s
for i in range(n):
if isOushu(i):
s1.append(s[i])
l1.append(i)
else:
s2.append(s[i])
l2.append(i)
s1.sort()
s2.sort()
sn1,sn2 =len(s1),len(s2)
for i in range(sn1):
inx = l1[i]
vua = s1[i]
ns[inx] =vua
for i in range(sn2):
inx = l2[i]
vua = s2[i]
ns[inx] =vua
#3、转换
base='0123456789abcdefABCDEF'
rs =''
for i in ns:
if i in base:
bstr =bin(int('0x'+i,16))[2:].rjust(4,'0')[::-1]
hstr =hex(int(bstr,2))[2:].upper()
rs+=hstr
else:
rs+=i
print(rs)
except:
break