fun main(args: Array<String>) {
    readLine()!!
    val guzaiValue = readLine()!!.split(" ").map { it.toDouble() }
    print(abc138c(guzaiValue))
}

fun abc138c(value: List<Double>):Double{
    var list = value.sorted().toMutableList()

    while( list.size >= 2){
        list.add((list[0] + list[1]) / 2)
        list = list.drop(2).toMutableList()
        list = list.sorted().toMutableList()
    }

    return list.first()
}