题解 | #提取不重复的整数#

import sys

#for line in sys.stdin:
 #   a = line.split()
 #   print(int(a[0]) + int(a[1]))


s=input()
s=s[::-1]
L=[]
for i in s:
    if i not in L:
        L.append(i)
print("".join(L))