// A - Pair
// https://abc108.contest.atcoder.jp/tasks/abc108_a

import scala.io.StdIn.readLine

object Main extends App {

  val k = readLine.toInt

  val halfFloor = k / 2
  val (odd, even) = if (k % 2 == 0) (halfFloor, halfFloor) else (halfFloor + 1, halfFloor)

  val c = odd * even

  println(c)

}