If entering the Gmail information from the locked screen does not allow you access, you will need to perform a Factory Data Reset using the alternate method by pressing a series of button pressings. Google 'how do I hard reset *insert your phone model name*'. Look for the alternative methods. Sadly, all information on the phone will be erased, with no recovery. Info on the SD will remain intact. Your contacts will come back from whatever backup your carrier provides (hopefully) and hopefully you know your gmail login and password.
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