N = int(input())
A = list(map(int,input().split()))
A = sorted(A)
Asum = sum(A)
J = N%2
B = N

if J == 0:
    B -= 1
    print(Asum/2**B)
elif Asum == A[0]*N:
    print(A[0])
else:
    B -= 2
    print((((Asum-A[N-1])/(2**B))+A[N-1])/2)