#ACB138 C1

N=int(input())

V=list(map(int,input().split()))


def merge(mylist):
	mylist=sorted(mylist)
	curval=0
	curlist=[]
	if len(mylist)<2:
		return mylist[0]

	curval = mylist[0]+mylist[1]
	curlist.append(curval/2)
	if len(mylist) %2 !=0:
		curlist.append(mylist[-1])
	return merge(curlist)

print(merge(V))