[<AutoOpen>]
module Program

open System

let read f = stdin.ReadLine() |> f
let reada f = stdin.ReadLine().Split() |> Array.map f
let reads f = stdin.ReadLine().Split() |> Array.toList |> List.map f

[<EntryPoint>]
let main _ =
    let n = read int
    let vs = reads float

    let rec loop xs =
        match List.sort xs with
        | [] -> failwith "error"
        | [y] -> y
        | y :: z :: zs ->
            loop (((y + z) / 2.0) :: zs)

    printfn "%.6f" (loop vs)
    0