
object Main extends App {
  val sc = new java.util.Scanner(System.in) 
  sc.useDelimiter("\n")
  val n = sc.nextInt()
  val d = sc.next().split(" ").map(_.toDouble).toList.sorted
  val ans = d.foldLeft(d(0))((x, y) => (x + y) / 2)
  println(ans)
}