N=int(input())
A=input().split(" ")
A=[int(i) for i in A]
A.sort()

def yo(A):
  ans=A[0]/(2*(len(A)-1))
  for i in range(1,len(A)):
    ans+=A[i]/(2*(len(A)-i))
  return ans

def act(A):
  if len(A)%2==0:
    A_=[]
    for i in range(int(len(A)/2)):
      A_.append((A[2*i]+A[2*i+1])/2)
    return A_
  
  elif len(A)%2==1:
    A_=[]
    for i in range(int((len(A)-1)/2)):
      A_.append((A[2*i]+A[2*i+1])/2)
    A_.append(A[len(A)-1])
    return A_
    
li=[]
while len(A)>1:
  li.append(yo(A))
  A=act(A)

li.append(A[0])
print(max(li))