defmodule Main do
  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)
  def yn(b), do: IO.puts(if b, do: "Yes", else: "No")

  import Bitwise

  def main do
    [f0, f1, n] = li()

    a = [f0, f1, bxor(f0, f1)]
    Enum.at(a, rem(n, 3))
    |> IO.puts
  end
end