1.hs

import Criterion.Main

import System.Environment
import qualified Data.Vector.Unboxed as V

magicHere :: Int -> Int
magicHere n = V.sum (V.take n p1)
  where
    p1 = V.unfoldr (\(c,s) -> let k = c+s in k `seq` Just (k,(c+1,k))) (0,1) 

helper n = magicHere n

main = do
  n <- fmap (read . head) getArgs
  print $ magicHere n
  putStrLn "Happy Me!"
{-
  defaultMain
    [ bench "magic-here"      $ nf helper    n]
-}