object Main extends App {
  val nxtInput = scala.io.StdIn.readLine()
  val nxtArray = nxtInput.split(" ").map(_.toInt).toVector

  val n = nxtArray(0)
  val x = nxtArray(1)
  val t = nxtArray(2)
  var tempKosuu = 0
  var result = 0

  while(n > tempKosuu) {
    tempKosuu = tempKosuu + x
    result = result + t
  }
  println(result)
}