object Main {
  def main(args: Array[String]): Unit = {
    val scanner = new java.util.Scanner(System.in)
    val input = scanner.nextLine().toInt
    def get_number_of_divisors(num: Int, next_cadidates:Int, acc: Int):Int = {
      if(next_cadidates*next_cadidates > num)
        acc
      else if(next_cadidates*next_cadidates == num)
        get_number_of_divisors(num, next_cadidates+1, acc+1)
      else if(num % next_cadidates == 0)
        get_number_of_divisors(num, next_cadidates+1, acc+2)
      else
        get_number_of_divisors(num, next_cadidates+1, acc)
    }
    println((1 to input).map(n=>n*get_number_of_divisors(n, 1, 0)).sum)
  }
}