import java.util.*

fun main(args: Array<String>) {
    val scanner = Scanner(System.`in`)
    val n = scanner.nextInt()
    val array = Array(n, {0.0})
    for(i in 0..n-1){
        array[i] = scanner.nextDouble()
    }
    array.sortDescending()
    val array2 = Array(n-1, {0.0})
    for(i in 1..n-1){
        array2[i-1] = array[i]
    }
    array2.sort()
    var result = array2[0]
    for(i in 1..array2.size-1){
        result = (result+array2[i])/2.0
    }
    println((array[0]+result)/2.0)
}