Problem

Statement

You are given a string of length , containing occurrences of a and occurrences of b.
You will choose some of the characters in . Here, for each , it is not allowed to choose exactly one of the following two: the occurrence of a and the occurrence of b. (That is, you can only choose both or neither.) Then, you will concatenate the chosen characters (without changing the order).
Find the lexicographically largest string that can be obtained in this way.

Constraints

is a string of length containing occurrences of a and occurrences of b.

Input

Input is given from Standard Input in the following format:

Output

Print the lexicographically largest string that satisfies the condition.

Sample

Input #1

Output #1

Explanation #1
A subsequence of obtained from taking the first, third, fourth and sixth characters in , satisfies the condition.
Input #2

Output #2

Explanation #2
You can choose all the characters.
Input #3

Output #3

Input #4

Output #4

Code

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