Make Alternating String

You are given a string s consisting of only the characters 'a' and 'b'. Your task is to remove the minimum number of characters from s so that the resulting string is alternating, meaning no two adjacent characters are the same.

An alternating string is defined as a string where every pair of consecutive characters are different. For example, both "abab" and "baba" are alternating strings, whereas "aab" is not.

Note: It is guaranteed that the input string contains only the characters "a" and "b".

Mathematical Expression: The problem can be formalized as follows. Given a string \( s = s_1s_2\dots s_n \) where \( s_i \in \{a, b\} \), find a subsequence \( s' \) of \( s \) such that \( s' \) is alternating and \( |s| - |s'| \) is minimized.

inputFormat

The input is read from standard input. It consists of a single line that contains the string s which only includes lowercase characters a and b. The string may be empty.

outputFormat

Print the resulting alternating string to standard output.

## sample

aab

ab

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