import scala.io.StdIn
object Main extends App {
  def avg(a: Double, b: Double): Double = { (a + b)/2.0 }
  val N = StdIn.readLine()
  val Vs = StdIn.readLine().split(" ").map(_.toDouble).toList.sorted
  println(Vs.tail.foldLeft(Vs.head)(avg))
}
