fun main(args: Array<String>){
  val k: Int = readLine()!!.toInt()
  var c: Int = 0
  for(i in 1..k){
    for(j in i..k){
      if(i % 2 == 0) if(j % 2 == 1) c++;
      else           if(j % 2 == 0) c++;
    }
  }
  println("$c")
}