defmodule Main do
  def main do
    IO.read(:line)
    |> String.trim()
    |> solve
    |> IO.puts()
  end

  defp solve(n) do
    n
    |> String.slice(1..-1)
    |> (fn o ->
          s = o |> String.length()
          t = o |> String.to_charlist() |> Enum.count(&(&1 == ?3))

          cond do
            n |> String.first() != "1" || s != t || t == 0 -> -1
            true -> s
          end
        end).()
  end
end