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")

  def main do
    [a, b, c, d] = li()

    t = abs(a - c) + abs(b - d)
    cond do
      t <= 3 -> 1
      a == c or b == d -> 1
      true -> 2
    end
    |> IO.puts
  end
end