fun readStr () =
    let
        fun scan reader stream = SOME (StringCvt.splitl (not o Char.isSpace) reader (StringCvt.skipWS reader stream))
    in
        valOf (TextIO.scanStream scan TextIO.stdIn)
    end


fun intString n =
    if 0 <= n
    then Int.toString n
    else "-" ^ Int.toString (abs n)


fun findAns n =
    let
        val exploded = String.explode n
        val first = List.hd exploded
        val threes = List.tl exploded

        exception NotThree
        fun findAnsAux nil = 0
          | findAnsAux (#"3" :: tl) =
            1 + findAnsAux tl
          | findAnsAux (_ :: _) =
            raise NotThree
    in
        if first = #"1"
        then
            (
              (findAnsAux threes)
              handle NotThree => ~1
            )
        else
            (
              ~1
            )
    end


val () =
    let
        val n = readStr ()
        
        val ans = findAns n
    in
        print (intString ans ^ "\n")
    end