def trans(c):
    ls = ['0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f','A','B','C','D','E','F']
    if c not in ls:
        return c
    res = str(bin(int(c,16))[2:])
    res = res.rjust(4,'0')
    return hex(int(res[::-1],2))[2:].upper()

def sortstr(s):
    odd,even = [],[]
    for i,v in enumerate(s):
        if i%2 == 0:
            even.append(v)
        else: odd.append(v)
    even.sort()
    odd.sort()
    res = ''
    for i in range(len(s)):
        if i%2 == 0:
            res += even.pop(0)
        else:res += odd.pop(0)
    return res


s = input().replace(' ','')
news = sortstr(s)
result = ''
for c in news:
    result += trans(c)
print(result)