import Control.Applicative
import Data.Tree
import Data.Foldable (toList)
import System.Environment

type Node = Tree ()

make_tree depth
    | depth > 1 = Node () [ make_tree (depth-1)
                          , make_tree (depth-1) ]
    | otherwise = Node () []
    
counter = length . toList . make_tree

main   = do depth <- depthArg <$> getArgs
            print $ counter depth
    where depthArg [] = 10
          depthArg  lst = read . head $ lst