import java.util.*
fun main(arg: Array<String>) {
    val N = nextInt()
    val V = listOfDouble()
    var Q = PriorityQueue<Double>(N, Comparator { a, b ->  a.compareTo(b) })
    Q.addAll(V)
    for (n in 1..N - 1) {
        val v1 = Q.poll()
        val v2 = Q.poll()
        Q.add((v1 + v2) / 2)
    }
    println(Q.peek())
}
fun next() = readLine()!!
fun nextInt() = Integer.parseInt(next())
fun listOfString() = next().split(" ")
fun listOfDouble() = listOfString().map { java.lang.Double.parseDouble(it) }