import string
str1 = string.ascii_letters
while True:
    try:
        data1 = input()
        data2 = []
        for word in data1:
            data2.append(ord(word))
#         #冒泡排序法
#         for m in range(1,len(data2)):
#             for n in range(0,len(data2)-m):
#                 if data2[n] > data2[n+1]:
#                     temp = data2[n]
#                     data2[n] = data2[n+1]
#                     data2[n+1] = temp
        data2.sort()
        data3 = []
        for word in data2:
            data3.append(chr(word))
        print(''.join(data3))
    except:
        break