import System.Environment
import qualified Data.Adaptive.List as L
import qualified Data.Adaptive.Tuple as L

main = do
    [n] <- mapM readIO =<< getArgs
    print $ L.maximum . L.take (n-1) . L.map (\p -> L.pair (L.fst p *2) (L.snd p *4)) $
        L.zip
            (L.replicate n n     :: L.List Int)
            (L.replicate (n-1) n :: L.List Int)