import qualified Data.ByteString.Char8 as B

main :: IO ()
main = do
  s <- B.getLine
  B.putStrLn $ f s

pickOdds
  :: [a] -> [a]
pickOdds = map snd . filter fst . zip (cycle [True, False])

f as = B.pack [ x | let l = B.length as
                  , i<- [0,2 .. l-1]
                  , let x = B.index as i ]
