I want to study computer science at university but dont do FM.

I really want to do computer science at top universitys ( preferablly ) and I do maths, physics and cs. I am in year 12 currently. What are my options? What can I, and should I do? I was considering redoing and doing year 12 again with FM if my school allows it. Or try my luck with just normal maths? But I'd like to go to a really good university. Any advice?