Researchers are looking for new treatments for HIV-1 (human immunodeficiency virus type 1) that are safe, well-tolerated, and can be taken less often. HIV-1 is the most common type of HIV, which is a virus that attacks cells of the immune system. Ulonivirine (MK-8507) is a study medicine designed to treat HIV-1 The goal of this study is to learn if ulonivirine does not increase the QT interval (a measure of heart rhythm on an electrocardiogram) above a certain amount. Researchers also want to learn what happens to the amount of ulonivirine in a healthy person's body over time.