object Main extends App {
  @scala.annotation.tailrec
  def loop(v: Double, vs: Seq[Double]): Double = {
    vs match {
      case Seq() => v
      case head::tail => loop((v + head) / 2, tail)
    }
  }
  val sc = new java.util.Scanner(System.in)
  val v::vs = List.fill(sc.nextInt())(sc.nextDouble()).sorted
  println(loop(v, vs))
}