defmodule Main do
  def main do
    IO.read(:line)
    |> String.trim()
    |> String.to_integer()
    |> solve()
    |> IO.puts()
  end

  def count_divisors(n) do
    1..(:math.sqrt(n) |> floor)
    |> Enum.reduce(0, fn i, acc_count ->
      if rem(n, i) == 0 do
        if div(n, i) == i do
          acc_count + 1
        else
          acc_count + 2
        end
      else
        acc_count
      end
    end)
  end

  def solve(n) do
    1..n
    |> Enum.reduce(0, fn k, acc_answer -> acc_answer + k * count_divisors(k) end)
  end
end