N=int(input())
A=list(map(int,input().split()))
B=list(sorted(A))
c=B.pop(0)
m=N-1
total=0
if N==2:
    max=sum(A)/2
elif N>2:
    for a in range(0,m):
        total+=B[a]/(2**(m-a))
    max=total+c/(2**N)

print(max)
  
  
  