import sys

def convert(in_str):
    lst = []
    for i in in_str:
        lst.append(ord(i))
    lst.sort()
    res = ''
    for item in lst:
        res += str(chr(item))
    return res

while True:
    try:
        in_str = sys.stdin.readline().strip()
        if in_str == '':
            break
        print(convert(in_str))
    except:
        break