思路：

代码：

a,b = map(str,input().split())
c = a+b
odds = []
evens = []
flag = 1
for i in range(len(c)):
    if flag == 1:
        evens.append(c[i])
        flag = 0
    else:
        odds.append(c[i])
        flag = 1

evens = sorted(evens)
odds = sorted(odds)
num = []
if len(evens) == len(odds):
    for i in range(len(evens)):
        num.append(evens[i])
        num.append(odds[i])
else:
    for j in range(len(evens)-1):
        num.append(evens[j])
        num.append(odds[j])
    num.append(evens[-1])
nums = list(num)
for i in range(len(nums)):
    if nums[i] in '0123456789abcdefABCDEF':
        nums[i] = format(int(nums[i],16), 'b')
        if len(nums[i]) < 4:
            nums[i] =  ('0' * (4-len(nums[i]))) + nums[i]
        nums[i] = nums[i][::-1]
        nums[i] = format(int(nums[i],2),'x').upper()
    print(nums[i],end='')