module Main where

import Control.Monad (when)
import Control.Monad.IO.Class (liftIO)
import Data.IORef (newIORef, readIORef, writeIORef)

import Procedural (for_)

main :: IO ()
main = do
  n <- newIORef (0 :: Int)
  for_ [1 .. 9] $ \i exit -> do
    n' <- liftIO $ readIORef n
    let n'' = n' + i
    when (n'' > 40) exit
    liftIO $ writeIORef n n''
  n' <- readIORef n
  print n'