defmodule Main do 
  def main do
    IO.stream(:stdio, :line) |> Enum.take(3) |> Enum.map(&String.trim/1)|> Enum.map(&String.to_integer/1) |> count |> IO.puts
  end
  
  def count([0, 0, _]) do
    0
  end
  
  def count([0, y, l]) when y > 0 do
    y/l |> abs |> ceil |> trunc
  end
  
  def count([0, y, l]) do
    y/l |> abs |> ceil |> trunc |> (fn num -> num + 2 end).()
  end

  def count([x, 0, l]) do
    x/l |> abs |> ceil |> trunc |> (fn num -> num + 1 end).()
  end

  def count([x, y, l]) do
    count([0, y, l]) + count([x, 0, l]) + rotate(x,y)
  end
  
  def rotate(_,y) when y > 0 do
    0
  end
  
  def rotate(_,_) do
    -1
  end
end