Public Class Program
  Shared Sub Main()
    Dim n As Integer = Integer.Parse(Console.ReadLine())
    Dim arrayV As Double() = Array.ConvertAll(Of String, Double)(Console.ReadLine().Split(" "), AddressOf Double.Parse)
    For i As Integer = 0 To n - 2
      Array.Sort(arrayV)
      Dim s As Double = (arrayV(i) + arrayV(i + 1)) / 2
      arrayV(i) = 0
      arrayV(i + 1) = s
    Next
    Console.WriteLine(arrayV(n - 1).ToString())
  End Sub
End Class