Calculate PI in less than 20 lines of code.

done = false
-- The algorithm will be ran 1/2 of the amount variable.
amount = 1000
x = 3
numpi = 1
while x < amount do
numpi = numpi - 1/x
x = x + 2
numpi = numpi + 1/x
x = x + 2
print(numpi * 4)
end
if x > amount and done == false then
numpi = numpi * 4
print(numpi)
print("Depending on how big the 'amount' variable is, is how accurate PI is")
done = true
end
stop = io.read()