How to unlock passcode if iphone 5?

Suddenly my iphone 5 showing that this phone has been stolen and it requires passcode to unlock.
i don't know what to do… Please help me… :'

You probably bought the phone from someone, the only way to get it unlock is to contact the original owner and ask them to remove it from their icloud account. Here's the link to apple tutorial you can send to the original owner.http://support.apple.com/kb/HT5661