Modify the String

Delete repeated characters until all characters are distinct, and return the lexicographically largest order-preserving result.

See "Input" for the standard input/output conventions and constraints added by this site.

输入格式

A lowercase string of length 1..100000.

输出格式

Output the largest deduplicated subsequence.

样例 1

输入：

aabcb

输出：

acb

样例 2

输入：

bcabc

输出：

cab

样例 3

输入：

aaaa

输出：

a

样例 4

输入：

cbacdcbc

输出：

cbad