规则Rules：
标准数独基础上，箭头格为N，箭头指向N+1。
Classic rules applied. Additionally, number N in arrow cell, N+1 in the direction the arrow points.
◆例题 Example
◆在线涂鸦 Draw it Online
◆在线做 Do it by CTC
◆在线做 Do it by Penpa
