object Main extends App {
  val inputs: Seq[String] = scala.io.Source.stdin.getLines().toList
  val n = inputs.head.toInt

  println(solve(n))

  def solve(n: Int): Long = {
    val nums = scala.collection.mutable.ArrayBuffer.fill(n+1)(0)
    var ans = 0L

    (1 to n).foreach { i =>
      (1 to i).foreach { j =>
        if (i % j == 0) nums.update(i, nums(i) + 1)
      }
    }

    (1 to n).foreach { i =>
      ans = ans + nums(i) * i
    }
    return ans
  }
}
