Adjacent Twins

easy
1. Given a string S of lowercase letters, a duplicate removal consists of choosing two adjacent and equal letters, and removing them.
 2. We repeatedly make duplicate removals on S until we no longer can.
 3. Return the final string after all such duplicate removals have been made.  
 4. It is guaranteed the answer is unique.    
 
 Example
 Input: "abbaca"
 Output: "ca"
 Explanation: 
 For example, in "abbaca" we could remove "bb" since the letters are adjacent and equal, and this is the only possible move.  
 The result of this move is that the string is "aaca", of which only "aa" is possible, so the final string is "ca".

Input Format

A String

Output Format

A string

Constraints

1 <= S.length <= 20000
 S consists only of English lowercase letters.

Notice

Try First, Check Solution later

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2. Think of a solution approach, then try and submit the question on editor tab.
3. We strongly advise you to watch the solution video for prescribed approach.

Example

Input
abbaca
Output
ca
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