object Main extends App {
  import scala.collection.mutable.PriorityQueue
  val sc = new java.util.Scanner(System.in)
  val N = sc.nextInt
  val Vs = List.fill(N)(sc.nextInt)
  val pq = new PriorityQueue[Float]()(Ordering.Float.reverse)
  Vs.foreach(pq += _)
  for(_ <- 1 to N - 1){pq += (pq.dequeue + pq.dequeue)/2}
  println(pq.head)
}