object Main{
  def main(args: Array[String]) ={ 
    val N = io.StdIn.readLine().toLong
    val v = io.StdIn.readLine().split(' ').map(_.toDouble).sorted

    val value = v.reduce{
      (lhs, rhs) =>
        (lhs + rhs) / 2.0
    }

    println(value)
  }
}