You would need to put down whatever the expiration date on the I-94 indicates.  Typically for the F-1 it shows as D/S, duration of status, and that is what you would indicate if that's the case in your situation.  There should not be an issue if you are adjusting status on the basis of a bona fide marriage to a US citizen.  Please let me know if you have any additional questions or need assistance with this matter.