defmodule Main do
  def main do
    [{x, _}, {y, _}] = IO.read(:line) |> String.split() |> Enum.map(&Integer.parse/1)
    [{x2, _}, {y2, _}] = IO.read(:line) |> String.split() |> Enum.map(&Integer.parse/1)

    solve(x, y, x2, y2)
    |> IO.puts()
  end

  def solve(x, y, x2, y2) do
    cond do
      x == 0 && y2 < y -> y
      y == 0 && x2 < x -> x
      x == y && x2 == y2 && x2 < x -> x + 1
      :else -> max(x, y)
    end
  end
end