n = input()
back = []
# for i in range(len(n)-1,-1,-1):
#     if n[i] not in back:
#         back.append(n[i])
#     else:
#         i -= 1
# result = ''.join(back)
# print(int(result))
for str in reversed(n):
    if str not in back:
        back.append(str)
result = ''.join(back)
print(int(result))

倒序检查字符是否重复出现，将不重复的入栈，最后将字符串转为数字