N = int(input())
V_list = list(map(int, input().split()))


import heapq

heapq.heapify(V_list)


for i in range(N-1):
        v1=heapq.heappop(V_list)
        v2=heapq.heappop(V_list)
        new_v = (v1+v2)/2
        heapq.heappush(V_list,new_v)





print(V_list[0])
~