这道题实在算不上【较难】,比【中等】的购物单简单太多了

#简单模拟题
s1=input().replace(" ","")
s2=s1[::2]#偶数位
s3=s1[1::2]#奇数位
s2=sorted(s2)
s3=sorted(s3)
s1=""
for i in range(len(s2)):
    try:#避免越界报错
        s1+=s2[i]
        s1+=s3[i]
    except:
        break
s4=""
for i in s1:
    if "0"<=i<="9" or "A"<=i<="F" or "a"<=i<="f":
        a=int(i,16)
        b=("0"*(4-len(bin(a)[2:]))+bin(a)[2:])[::-1]#倒序字符串,注意补0
        b=int(b,2)#转为十进制数
        c=hex(b)[2:]#转为16进制
        if c.isalpha():
            c=c.upper()
        s4+=c
    else:
        s4+=i
print(s4)