二分找 24 落在哪个下标

运行下面这段程序：

def bfind(a, target):
    lo = 0
    hi = len(a) - 1
    while lo <= hi:
        mid = (lo + hi) // 2
        if a[mid] == target:
            return mid
        if a[mid] < target:
            lo = mid + 1
        else:
            hi = mid - 1
    return -1

print(bfind([13, 15, 17, 23, 24], 24))