main :: IO ()
main = do
  s <- getLine
  putStrLn $ pickOdds' s

pickOdds, pickOdds'
  :: [a] -> [a]
pickOdds []       = []
pickOdds [a]      = [a]
pickOdds (a:b:bs) = a : pickOdds bs 

pickOdds' = map snd . filter (odd . fst) . zip [1..]