import java.util.*

fun main(args: Array<String>) {
    val n = readLine()?.toInt() ?: return
    val v = readLine()?.split(" ")?.map(String::toDouble) ?: return
    val q = PriorityQueue(v)
    while(q.size > 1){
        val a = q.poll()
        val b = q.poll()
        q.offer((a+b)/2)
    }
    println(q.poll())
}