import scala.io.StdIn._

object Main extends App {
  val N = readInt()
  val ingredients = readLine().split(" ").map(_.toDouble).toBuffer.sorted

  while (ingredients.length > 1) {
    val mixed = (ingredients.head + ingredients.tail.head) / 2
    ingredients.trimStart(2)
    ingredients.+=:(mixed).sorted
  }

  val ans = ingredients.head
  
  println(ans)
}
