import scala.io.StdIn._

object Main extends App {
  val N = readInt().toDouble
  val ingredients = readLine().split(" ").map(_.toDouble)
  var buf = collection.mutable.ArrayBuffer(ingredients: _*).sortWith(_ < _)

  while (buf.nonEmpty) {
    if (buf.size == 1) {
      println(buf.head); sys.exit()
    }
    val acc = (buf(0) + buf(1)) / 2
    buf = buf.drop(2)
    buf = (buf :+ acc).sortWith(_ < _)
  }
}
