import java.io.PrintWriter

fun solve(out: PrintWriter): Boolean = with(out) {
    readLine()!!
    // ASC
    val vs = readLine()!!.split(" ")
        .map{ it.toDouble() }
        .sorted()

    var ans = vs[0]
    vs.drop(1)
    for (v in vs) {
        ans += v
        ans /= 2.0
    }

    println(ans)
    return false
}

fun main(args: Array<String>) = with(PrintWriter(System.out)){
    while(solve(this));
    flush()
}