How many caffeine pills can i safely take?

I got some of those caffeine pills made by walgreens, the "stay awake" brand. Each pill is 200 mg which according to the box is about the same as a cup of coffee. The directions say take one but i was wondering if it would be that bad to take 2 or even 3 at once. I know caffeine in excessive amounts can actually kill you because it causes the heart to beat so fast it suffers from ventricular fibrillation and goes into cardiac arrest. I guess my question is does anyone know how many caffeine pills you can safely take without risking such a thing?