import scala.annotation.tailrec

object Main extends App {
  val sc = new java.util.Scanner(System.in)
  val n = sc.nextInt

  val i1 = (1 to Math.sqrt(n).toInt).map(i => loopJ(i, i + 1, 0)).sum
  val i2 = loopI(1, 0)
  //println(i1)
  //println(i2)
  println(i1 * 2 + i2)

  @tailrec
  def loopJ(i: Int, j: Int, count: Int): Int = {
    if (i * j < n) {
      //println(i + " " + j)
      loopJ(i, j + 1, count + 1)
    } else {
      count
    }
  }

  @tailrec
  def loopI(i: Int, count: Int): Int = {
    if (i * i < n) {
      //println(i + " " + i)
      loopI(i + 1, count + 1)
    } else {
      count
    }
  }

}
