import java.util.Scanner

object Main {
  def main(args: Array[String]): Unit = println(solve(new Scanner(System.in)))

  def solve(in: String): String = solve(new Scanner(in))

  def solve(sc: Scanner): String = {
    val K = sc.nextInt

    val ke = K / 2
    val ko = if (K % 2 == 0) K / 2 else K / 2 + 1
    (ke * ko).toString
  }
}
