属主自己就能修，不用惊动 root

运行下面这段程序，填写它打印出来的结果。

def cls(uid, gid, f_uid, f_gid):
    if uid == f_uid:
        return 0
    if gid == f_gid:
        return 1
    return 2

def can(mode, k, op):
    digit = (mode >> (3 * (2 - k))) & 7
    bit = {"r": 4, "w": 2, "x": 1}[op]
    return digit & bit != 0

mode = 0o044
before = can(mode, 0, "r")
after = can(mode | 0o400, 0, "r")
print(str(before) + "/" + str(after))