CF125B Simple XML

Let's define a string as an opening tag, where $ x $ is any small letter of the Latin alphabet. Each opening tag matches a closing tag of the type , where $ x $ is the same letter. Tegs can be nested into each other: in this case one opening and closing tag pair is located inside another pair. Let's define the notion of a XML-text: - an empty string is a XML-text - if $ s $ is a XML-text, then $ s' $ =+ $ s $ + also is a XML-text, where $ a $ is any small Latin letter - if $ s_{1} $ , $ s_{2} $ are XML-texts, then $ s_{1} $ + $ s_{2} $ also is a XML-text You are given a XML-text (it is guaranteed that the text is valid), your task is to print in the following form: - each tag (opening and closing) is located on a single line - print before the tag $ 2*h $ spaces, where $ h $ is the level of the tag's nestedness.

The input data consists on the only non-empty string — the XML-text, its length does not exceed 1000 characters. It is guaranteed that the text is valid. The text contains no spaces.

Print the given XML-text according to the above-given rules.