{-# LANGUAGE NoMonomorphismRestriction #-}

module Main where

import Data.Monoid
import Control.Applicative
import Control.Monad.Writer.Strict
import Control.Monad              
import System                     

data Tree = Node [Tree]

inc = tell (Sum 1)

node x = inc >> return (Node x)

make 0 = node []
make depth = replicateM 2 (make (depth -1)) >>= node

main = do
  depth <- depthArgs <$> getArgs
  let counter = getSum . execWriter . make $ depth
  print counter
    where
      depthArgs :: [String] -> Int
      depthArgs [] = 10
      depthArgs [x] = read x