fun main(args: Array<String>) {
  readLine()
  val list: List<Int> = readLine()!!.split(" ").map { it.toInt() }
  list.sort()
  var ans: Float = (list[0] + list[1]) / 2
  for(int i = 2; i < list.size(); i++) {
    ans = (ans + list[i]) / 2
  }
  println(ans)
}