object Main {
  def main(args: Array[String]): Unit = {
    val Array( need_num, create_num, create_time ) = scala.io.StdIn.readLine.split( " " ).map{ _.toInt }
    var total_time = ( need_num/create_num )*create_time
    if( need_num%create_num != 0 ) total_time += create_time
    println( total_time )
  }
}