How much time do I still have

How much time do I still have
 

In the exam hall, if I have not brought a watch with me and I want to know the time left for me to finish the exam, what can I say to ask those invigilators?

??How much time do I still have??

Are there other ways of expressing the same meaning?

An alternate question: "How much time is left?" :)

How much time do I still have?
How much time is left?
How much time remains?

You can also say: When is my time up?

Thank you!