import Control.Applicative ((<$>))
import Data.ByteString.Char8 (ByteString)
import qualified Data.ByteString.Char8 as B

main :: IO ()
main = print =<< solve <$> B.getLine

solve :: ByteString -> Int
solve bs
    | (B.head bs) /= '1' = -1
    | B.length bs == 1   = -1
    | otherwise          = B.foldl' (\acc -> \x -> if x /= '3' then (-1) else if acc == (-1) then (-1) else acc + 1) 0 $ B.tail bs