n = int(input())
value = [int(i) for i in input().split()]

now = 0
a = sorted(value)

while len(a) >= 2:
  new = sorted(a)
  
  now = (float(a[0]) + float(a[1])) / float(2)
  if len(a) >= 3:
    del a[0],a[0]
    a.append(now)
  elif len(a) == 2:
    print(now)
    break