{-# LANGUAGE BangPatterns #-}
module Main where


data D = C { x :: !Int } deriving Show

f :: Int -> D
f 0 = C 0
f n =
  let !z = n + 1 in
  let !r = f z in
  let !(C {x = y }) = r in
  let !res = C { x = y } in
  res


main :: IO ()
main = do
  putStrLn $ show $ f 0
  putStrLn $ show $ f 1