import Control.Applicative
main = do
  ans <- map show . g . foldr f [0,0,0] . map read . drop 1 . words <$> getContents
  print $ (length ans) - 1
  putStrLn $ unwords $ ans
  where
    f i [a,b,c] = [i,a+c,b]
    g [a,0,0] = [a]
    g [a,b,0] = [a,b]
    g [a,b,c] = [a,b,c]