import java.util.*

fun main(args: Array<String>) {
    val k = Integer.parseInt(readNext())
    val s = readNext()
    val list = s.split(" ").map { Integer.parseInt(it) }
    val sortList = list.sorted()
    var result = sum(sortList, 0.0)


    println(result)
}
fun sum  (list: List<Int>, res: Double) : Double {
    if(list.isEmpty()) {
        return res
    }
    var resp: Double
    val ls:List<Int>
    if (res != 0.0){
        resp = (list.get(0).toDouble() + res) / 2
        ls = list.drop(1)
    } else {
        resp = (list.get(0).toDouble() + list.get(1)) / 2
        ls = list.drop(2)
    }
    return sum(ls, resp)
}

    fun readNext(): String {
        return readLine()!!
    }
