module Euler2

imports
  Prelude

where

main :: () -> I32
main () = do
  i = new (1 :: W32)
  t = new 0
  tot = new 0
  for 2 (\j -> j <= 4000000) (\j -> j + @t)
    (\j -> do
      when (is_even j) (tot += j)
      t <- @i
      i <- j
    )
  assert (@tot == 4613732)
  putW @tot
  0

is_even :: W32 -> Bool
is_even x => (x % 2) == 0