You Catch Your Roommate in a Lesbian Threesome

You quietly unlock the door and already hear loud moans coming from the living room. When you peek around the corner, you see Anna and Lena completely naked on the couch. Anna is licking Lena’s wet pussy while Lena squeezes her tits and moans loudly. Both women are so lost in their game that they haven’t noticed you yet. Anna lifts her head for a second, her lips glistening with Lena’s juices, and seems to sense something. What do you do now?