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
    input()
    a = li()

    gg = a |> group_by2(fn a, b -> a+1 == b end)
    for g <- gg, reduce: 0 do
      acc ->
        k = length(g)
        div(k * (k-1), 2) + acc
    end
    |> IO.puts
  end

  # def group_by2([], _pred), do: []
  # def group_by2(xs, pred) do
  #   n = Stream.chunk_every(xs, 2, 1, :discard)
  #   |> Stream.take_while(fn [a, b] -> pred.(a, b) end)
  #   |> Enum.count

  #   {a, b} = Enum.split(xs, n+1)
  #   [a | group_by2(b, pred)]
  # end


  def group_by2([], _pred), do: []
  def group_by2([x | xs], pred), do: _group_by2(xs, pred, [x])

  defp _group_by2([], _pred, acc), do: [Enum.reverse(acc)]
  defp _group_by2([x | xs], pred, acc) do
    if pred.(hd(acc), x) do
      _group_by2(xs, pred, [x | acc])
    else
      a = Enum.reverse(acc)
      [a | _group_by2(xs, pred, [x])]
    end
  end
end