import heapq

N = int(input())
a = list(map(int,input().split()))
while(True):
    if len(a)==1:
        print(a[0])
        break
    s1 = heapq.heappop(a)
    s2 = heapq.heappop(a)
    heapq.heappush(a,(s1+s2)/2)