import java.util.*

fun main(arr:Array<String>) {
    val n = readLine()!!.toInt()
    val numbers = readLine()!!.split(" ").map { it.toInt() }.sorted()
    val queue = PriorityQueue<Double>()
    queue.addAll(numbers.map { it.toDouble() })
    while (queue.count() > 2) {
        val current = (queue.poll() + queue.poll())/2
        queue.add(current)
    }
    val ans = (queue.poll() + queue.poll()) / 2
    println(ans)
}
