defmodule Main do
    def calc("", index) do
        index - 1
    end
    def calc(s, index) do
        x = String.first(s)
        xs = String.slice(s, 1..-1)
        calc(x, xs, index)
    end

    def calc("1", xs, 0) do
        calc(xs, 1)
    end
    def calc(_, _, 0) do
        -1
    end

    def calc("3", xs, index) do
        calc(xs, index + 1)
    end
    def calc(_, _, _) do
        -1
    end

    def main do
        s = IO.gets("") |> String.trim
        calc(s, 0) |> IO.puts
    end
end