how do I make this weird guy go away

Um so pretty self explanatory text. I'm 13 and im going to this fancy sleepaway camp in a university where we take uni courses (i'm taking pre calc honors <3) and everyone from grades 6-8 is on the same floor. I was in the lounge reading a book with my friend and then these 2 guys came in and they had this app that was like making whip noises if u whip ur phone. i told them to stop and one of the guys was like "sure ok" but the other one was like talking to me and being weird. So then he was like trying to show me a bunch of goofy yt videos and like talking to me abt math and i was like "plz just let me read my book in silence" but he wouldnt stop and it was so weird, so i just like made small talk and shit

Anyways I went to my room, then returned to the hallway to fill my water bottle, and he was there and was like weirdly staring at me and stuff, it makes me very uncomfortable and i dont think he'd listen to me if i told him to stop, i already kinda signaled that i wasnt interested in talking to him and stuff. my roommate thinks that he def likes me and its so weird, how do i make him go away bc he makes me so uncomfortable

Serious advice please

PS the book I was reading was the three body problem by cixin liu