弹一次之后还剩几个

同一个堆。运行下面这段程序：

def sift_down(h, i, n):
    while True:
        big = i
        l = 2 * i + 1
        r = 2 * i + 2
        if l < n and h[l] > h[big]:
            big = l
        if r < n and h[r] > h[big]:
            big = r
        if big == i:
            return
        h[i], h[big] = h[big], h[i]
        i = big

def pop(h):
    top = h[0]
    last = h.pop()
    if len(h) > 0:
        h[0] = last
        sift_down(h, 0, len(h))
    return top

h = [24, 23, 15, 13, 17]
pop(h)
print(len(h))