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