N = int(input())
v = list(map(int,input().split()))
v.sort()

while len(v) > 1:
  temp = []
  for i in range(len(v)//2):
    temp.append((v[2*i] + v[2*i + 1])/2)
  if len(v) % 2 == 0:
    v = temp
  else:
    temp.append(v[-1])
    v = temp
      
print(v[0]) 