import Data.Char
import Control.Applicative
import Control.Arrow

muntil p _ x | p x = return x
muntil p f x = f x >>= muntil p f

back = first . (++)

split (p:ps) = back [p] $ case p of
	']' -> ([], ps)
	'[' -> uncurry back $ second split $ split ps
	_   -> split ps
	
eval'    []  st = return ([], st)
eval' (p:ps) st = back [p] <$> case (p, st) of
	('>', (xs, y:ys)) -> eval' ps (y:xs, ys) 
	('<', (x:xs, ys)) -> eval' ps (xs, x:ys) 
	('+', (xs, y:ys)) -> eval' ps (xs, (y + 1):ys)
	('-', (xs, y:ys)) -> eval' ps (xs, (y - 1):ys)
	('.', (xs, y:ys)) -> putChar (chr y) >> eval' ps (xs, y:ys)
	(',', (xs, _:ys)) -> getChar >>= \y -> eval' ps (xs, ord y:ys)
	(']', st)         -> return (ps, st)
	('[', st)         -> do
		(ps', st') <- muntil (\(_, (_, y:_)) -> y == 0) (uncurry eval') (ps, st)
		let (pxs, pys) = split ps'
		back pxs <$> eval' pys st'
		
eval ps = eval' ps ([], repeat 0)

main = eval ">>+++++++[>++++++[>+<-]<-]+++++[>++[>>+<<-]<-]<<+++++[[>+>[-]>[-]<<[->+>+<<]>>[-<<+>>]<<>[>>.<<-]>>>.<<<<<-]]"