object Main {
  def main(args: Array[String]): Unit = {
    import scala.io.StdIn.readLine
    val Array(datN,datX,datT) = readLine.split(" ").map(_.toInt)

    val a = (datN / datX) + (if(datN % datX != 0) 1 else 0)

    val ans = a * datT
    println(ans)
  }
}
