How to insert Google Adsense into a Joomla/K2 article with JCE Editor

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This one has bugged me for a while. I could not find a way to insert the Javascript that holds Google adsense ads into joomla articles or K2 items. Because each time that I would save the article, the editor would strip out the javascript for security reasons. And so you would then loose your ad, or any other custom javascript.