defmodule Main do
  def main do
    IO.read(:line)

    IO.read(:line)
    |> String.trim()
    |> String.split()
    |> Enum.map(&String.to_integer/1)
    |> solve_rec(0)
    |> IO.puts()
  end

  def solve_rec([], x) do
    x
  end

  def solve_rec(a, x) do
    l = (a |> hd) - (a |> tl |> hd)
    r = (a |> Enum.at(-1)) - (a |> Enum.at(-2))

    cond do
      l < r -> solve_rec(a |> Enum.slice(0..-3), x + r)
      true -> solve_rec(a |> Enum.slice(2..-1), x + l)
    end
  end
end