n = int(input())
V = list(map(int, input().split()))
V.sort()
V.reverse()

if len(V) == 2:
  print(V[0]+V[1])/2
else:
  ans = 0
  for i in range(n-1):
    ans += V[i]/(2**(i+1))
  ans += V[n-1]/(2**(n-1))
  print(ans)