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 findAns [] = 0
  | findAns (#"0" :: tl) = findAns tl
  | findAns (_ :: tl) = 1 + findAns tl
                
                    
val () =
    let
        val c = readStr ()
        
        val ans = findAns (List.tl (String.explode c))
    in
        print (Int.toString ans ^ "\n")
    end