N = int(input())
v = input().split()
v.sort()
for i in range(N-1):
  x = (float(v[0]) + float(v[1])) / 2
  x = str(x)
  v.append(x)
  #print(v)
  if len(v) != 1:
    v.pop(0)
    v.pop(0)
  v.sort()
print(float(v[0]))