package main

import (
	"fmt"
	"sort"
)

func main(){
	var N int
	_ = fmt.Scan(&N)
	a := make([]int, N)
	for i :=0; i< N; i++{
		_ = fmt.Scan(&a[i])
	}
	sort.Sort(sort.IntSlice(a))
	var w float64
	w = float64(a[0]+a[1]) /2
	for i :=2; i < N; i++{
		w = (w+float64(a[i])) / 2
	}
	fmt.Println(w)

}