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

  def solve(n) when 0 <= n and n <= 100_000_000 do
    if rem(n, 2) == 0, do: n + 1, else: n
  end

end