规则Rules：
标准数独基础上，提示数周围四个数字中，有一个数字是其余三个数字的和。符合条件的情况被全部标记。
Classic rules applied. Additionally, around each black dot, one of the numbers is the sum of other three numbers. All cases fit this rule are all marked.
◆例题 Examples
◆在线涂鸦 Draw it Online
◆在线做 Do it by CTC
◆在线做 Do it by Penpa
