import java.util.*

fun main(args: Array<String>) {
    val n = readLine()!!.toInt()
    val v = readLine()!!.split(" ").map { it.toDouble() }
    var q = PriorityQueue(v)

    for (i in 1 until n){
        q.add((q.poll() + q.poll()) /2)
    }
    println(q.poll())
}