import java.util.Scanner

import scala.io.StdIn._
object Main extends App {

  val n = scala.io.StdIn.readInt()

  def solve(): Long = {
    val divisorCntArr = Array.fill(n + 1)(0L)
    for(i <- 1 to n) {
      for(j <- i to n by i) divisorCntArr(j) += 1
    }

    (1 to n).foldLeft(0L) { (acc, num) =>
      acc + (num * divisorCntArr(num))
    }
  }


  println(solve())

}

