n=int(input())
v=list(map(int,input().split()))
a=sorted(v)
if n==2:
    ans=(a[0]+a[1])/2
    print(ans)
    exit()
awase=(a[0]+a[1])/2
for i in range(3,n-1):
    awase=(awase+a[i])/2
awase=(awase+a[n-1])/2
print(awase)