import Control.Applicative ((<$>))
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B
import Data.List (unfoldr)
import Data.Char (isSpace)

main :: IO ()
main = getLine >> solve <$> (readil B.readInt <$> B.getLine) >>= mapM_ putStrLn

solve :: [Int] -> [String]
solve = f . reverse
  where f (0:rs) = f rs
        f [] = ["0", "0"]
        f [a] = ["0", show a]
        f [a, b] = ["1", show b ++ " " ++ show a]
        f [a, b, c] = ["2", show c ++ " " ++ show b ++ " " ++ show a]
        f (a:b:c:d:rs) = f (b:c+a:d:rs)

readil :: Integral a =>  (ByteString -> Maybe (a, ByteString)) -> ByteString -> [a]
readil f = unfoldr g
  where
    g s = do
      (n, s') <- f s
      return (n, B.dropWhile isSpace s')