import heapq

N = int(raw_input())
v = list(map(int,raw_input().split()))
heapq.heapify(v)
for i in range(0,N-1):
  v1 = heapq.heappop(v)
  v2 = heapq.heappop(v)
  
  heapq.heappush(v, (v1+v2)/float(2))
print v[0]