Pages 5 and 40 are missing and comic had originally 40 pages.
<h3>How to find the missing number of pages and the number of pages of the comic</h3>
Let suppose first that there are no more sheets beyond the sheet containing page 39. A sheet contains two pages, one <em>in front</em> and odd numbered and one <em>behind </em>and even numbered.
If two pages are missing, then another two are missing. According all assumptions, we conclude that pages 5 and 40 are missing and that comic had originally 40 pages.