A 40-year-old woman suddenly developed severe headache, occipital pain, and vomiting for 8 hours, without fever. No history of hypertension (HTN). Physical exam: alert, mild hypertension (BP). Right pupil dilated, absent pupillary light reflex, right upper eyelid ptosis, inability to move the eye upward, downward, and inward. Nuchal rigidity, Kernig's sign (+). Brain CT shows hyperdense signals in the interhemispheric fissure, lateral sulcus, and basal cistern. The affected cranial nerve is: