defmodule Main do
  def main do
    n = IO.gets("") |> String.trim |> String.to_integer
    Enum.reduce(1..n, 0, fn _x, acc -> sum(acc) end)
    |> IO.puts
  end
  def sum(acc) do
    n = IO.gets("") |> String.trim |> String.to_integer
    acc + n
  end
end