from heapq import heappush,heappop
n = int(input())
v = list(map(int,input().split()))

ans = 0
for i in range(n-1):
	a = heappop(v)
	b = heappop(v)
	ab = (a+b)/2
	ans += ab
	heappush(v,ab)
print(v[0])