N = int(input())
Vlist = list(map(int,input().split()))
while len(Vlist) > 1:
	Vlist.sort()
	min = 1000
	j = -1
	for i in range(0,len(Vlist)-1):
		if min > Vlist[i+1] - Vlist[i]:
			min = Vlist[i+1] - Vlist[i]
			j = i
	Vlist[j]=(Vlist[j]+Vlist[j+1])/2
	Vlist[j+1] = 0
	Vlist.remove(0)

print(Vlist[0])