defmodule Main do
  def main do
    # s = input()
    # ans = String.codepoints(s) |> Enum.map(&String.to_integer/1) |> Enum.sum

    x = ii()
    ans = Integer.digits(x) |> Enum.sum
    IO.puts ans
  end

  def input, do: IO.read(:line) |> String.trim
  def ii, do: input() |> String.to_integer
  def li, do: input() |> String.split |> Enum.map(&String.to_integer/1)
end