defmodule Main do
  #入力
  def main do
    num = IO.gets("") |> String.trim |> String.split |>Enum.map(&String.to_integer/1)
    check(num, 0)
  end
  # 大 小 中
  def check([a, b, c], cun) when a > b and a > c do
    if (a-c) < (c-b) do
      check([a-1, b, c], cun+1)
    else
      check([a, b, c-1], cun+1)
    end
  end
  # 中 小 大
  def check([a, b, c], cun) when a > b and a < c  do
    if (c-a) < (a-b) do
      check([a, b, c-1], cun+1)
    else
      check([a-1, b, c], cun+1)
    end
  end
  # 中 大 小
  def check([a, b, c], cun) when a > c and a < b do
    if (b-a) < (a-c) do
      check([a, b-1, c], cun+1)
    else
      check([a-1, b, c], cun+1)
    end
  end
  # 小 大 中
  def check([a, b, c], cun) when a < c and c < b do
      if (c-a) < (b-c) do
        check([a, b, c-1], cun+1)
      else
        check([a, b-1, c], cun+1)
      end
  end
  def check([a, b, c], cun) when a == b or a == c or b == c  do
    IO.inspect cun
  end
end