CF81A.Plug-in

Polycarp thinks about the meaning of life very often. He does this constantly, even when typing in the editor. Every time he starts brooding he can no longer fully concentrate and repeatedly presses the keys that need to be pressed only once. For example, instead of the phrase "how are you" he can type "hhoow aaaare yyoouu".

Polycarp decided to automate the process of correcting such errors. He decided to write a plug-in to the text editor that will remove pairs of identical consecutive letters (if there are any in the text). Of course, this is not exactly what Polycarp needs, but he's got to start from something!

Help Polycarp and write the main plug-in module. Your program should remove from a string all pairs of identical letters, which are consecutive. If after the removal there appear new pairs, the program should remove them as well. Technically, its work should be equivalent to the following: while the string contains a pair of consecutive identical letters, the pair should be deleted. Note that deleting of the consecutive identical letters can be done in any order, as any order leads to the same result.

波利卡普经常思考生命的意义。他总是这样，甚至在编辑器中输入文字时也不例外。每次他开始陷入沉思，就再也无法完全集中注意力，从而反复按下本应只按一次的键。例如，本该输入 “how are you”，他却可能输入成 “hhoow aaaare yyoouu”。

波利卡普决定将这类错误的修正过程自动化。他计划为文本编辑器编写一个插件，用于删除文本中所有相邻且相同的字母对（如果存在的话）。当然，这并非波利卡普真正需要的功能，但他总得从某个地方开始！

请帮助波利卡普编写该插件的核心模块。你的程序应当从字符串中移除所有相邻且相同的字母对。若移除后产生了新的相邻相同字母对，则也应继续移除。从技术上讲，其工作逻辑等价于以下过程：只要字符串中仍存在相邻且相同的字母对，就将其删除。注意：相邻相同字母对的删除顺序可以任意，因为任何顺序都会得到相同的结果。

The input data consists of a single line to be processed. The length of the line is from 1 to 2·105 characters inclusive. The string contains only lowercase Latin letters.

输入数据包含一行待处理的字符串。该行长度为 $1$ 至 $2 \cdot 10^5$ 个字符（含端点）。字符串中仅包含小写拉丁字母。

Print the given string after it is processed. It is guaranteed that the result will contain at least one character.

打印经过处理后的给定字符串。保证结果中至少包含一个字符。