import scala.math

object Main extends App {
  def divisors(n: Int): List[Int] =
    for (i <- (1 to n).toList if n % i == 0) yield i
  val sc = new java.util.Scanner(System.in)
  var n = sc.nextInt()
  var sum:BigInt = 0
  for (i <- 1 to n){
    sum += divisors(i).length*i
  }
  println(sum)
}
