A 36-year-old man who is HIV-positive presents to your clinic with a 6-week history of perianal burning and itching. Rectal examination reveals multiple small condylomata within the anal canal. Intraoperative excisional biopsies of the condylomata confirm human papillomavirus (HPV). Which of the following HPV subtypes confers the highest risk of anal high-grade dysplasia and squamous cell carcinoma?