规则Rules：
标准数独基础上，提示数是这一方向上前若干个数字之和。
Classic rules applied. Additionally, outside clue is the first several numbers' sum in this direction.
◆例题 Example
◆在线涂鸦 Draw it Online
◆在线做 Do it by CTC
◆在线做 Do it by Penpa
