N = int(input())
goods = list(map(int, input().split()))
print(goods)
if N == 2:
    print(sum(goods)/2)
else:
    while len(goods) > 2:
        goods = sorted(goods)
        a = goods.pop(0)
        b = goods.pop(0)
        goods.append((a+b)/2)
    print(sum(goods)/2)

        