N = int(input())
A = list(map(int,input().split()))
A = sorted(A)
Asum1 = sum(A)
Asum2 = sum(A)-A[N-1]
J = N%2
B = N

if J == 0:
    for _ in range(N//2):
        Asum1 /= 2
    print(Asum1)
else:
    for _ in range((N-1)//2):
        Asum2 /= 2
    Asum2 = (Asum2+A[N-1])/2
    print(Asum2)