from heapq import heappush, heappop, heapify

n = int(input())
values = list(map(int, input().split()))

heapify(values)

while len(values) > 1:
  a = heappop(values)
  b = heappop(values)
  heappush(values, (a+b) / 2)
  
print(values[0])
