n = int(input())
v_list = list(map(int,input().split()))
while len(v_list) >= 3:
  v_list.sort()
  new_v = (V_list[0] + v_list[1]) /2
  v_list.pop(0)
  v_list.pop(0)
  v_list.append(new_v)
print((v_list[0] + v_list[1]) / 2)
  