module Main
open System

let n = Console.ReadLine() |> int
let xs = Console.ReadLine().Split(' ')
        |> Array.map float
        |> Array.sort

Console.WriteLine(
    if n % 2 = 0 then
        let i =  n / 2
        (xs.[i] + xs.[i - 1]) / 2.0
    else
        xs.[n / 2]
)