规则Rules：
标准数独基础上，某个方向上第一个数字是X，提示表示前X格里的某个数字。
Classic rules applied. Additionally, when X is the first number in this direction, the clue shows one of the numbers in the first X cells.
作者Author：行连
◆在线做Do it by CTC
◆在线做 Do it by Penpa
