What happens if you implement both overriden OnInit() and Page_Init in a Page?

Hi to all. I do have a small doubt regarding ASP.NET Page Life Cycle events. When gone through the coding of an application i came to see both overriding of OnInit() method and also Page_Init event. I thought both the approaches serves the same purpose and i saw mostly the implementation of overriden OnInt() only but not both.Most of the articles in the web explains about the better approach in these two but no one explained what happens if we implement both. What does this situation means. Can anyone please help me regarding this. Thanks in Advance.