How to ask someone if i can sit with them at lunch?

i’m 15 in grade 11, i currently don’t like who i hang out with at lunch because they are just so mean to me but as they say “oh we’re just joking” but honestly i can’t stand them. i have no one else
i was wondering how i can work up the courage to ask someone if i can sit with them but idk how. i’m a very shy person
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