# boj, 1427 : 소트인사이드, python3
import sys
#N = list(map(str,input()))
N = list(map(str,sys.stdin.readline()))
result = []
for i in N:
result.append(i)
result.sort()
result.reverse()
print(''.join(result))
https://www.acmicpc.net/problem/1427