
import java.util.*

fun main (args:Array<String>) {
    val material = readLine()!!.toInt()
    val valueList = readLine()!!.split(" ").map(String::toDouble).sortedDescending()
    var stack = Stack<Double>()
    for (value in valueList){
        stack.push(value)
    }
    while (stack.size > 1){
        val a = stack.pop()
        val b = stack.pop()
        stack.push((a + b) / 2)
    }
    print(stack.pop())
}