cho.shWeb Pages
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You are probably familiar with HTML, the markup language used to create web pages. HTML code contains a number of tags, which are expected to follow certain rules.
In this problem we are concerned with two of these rules:
- Every opening tag must have a corresponding closing tag.
- All tags must be properly nested.
Tags are marked by angle brackets that contain a keyword, such as <body> or <strong>. These are opening tags; the corresponding closing tags place a / before the keyword, i.e. </body> and </strong>. A tag can be both opening and closing, such as <br />, which satisfies rule 1.
To be properly nested, if a tag is opened inside another tag, it must be closed before the outer tag closes. For example:
<body> <strong> </strong> </body>is properly nested.<body> <strong> </body> </strong>is not, and breaks rule 2.
If there are no tags present, the text complies with both rules.
Attributes may appear inside an opening tag, such as:
<a href="http://www.nzprogcontest.org.nz">This is a link</a>
A closing tag only has to match the keyword, not the attributes.
Input
The input consists of a number of lines of HTML code, each line containing from 0 to 255 characters. The last line contains a single # character — do not process this line. Each line contains zero or more tags. No angle bracket appears unless it is part of a properly formed tag.
For each line, determine whether or not it satisfies the rules described above. Each line is evaluated independently.
Output
The output consists of a single line for each line of input. Each line contains either the word legal or the word illegal.