规则Rules：
填入1~6，使得每宫内及每行列（三种方向上）数字不重复。每一宫或行列可能没有包含所有的数字。
Write 1~6, make numbers no repeated in each Box or each Row (in three directions). Each Box or Row may not contain all of the numbers.
◆在线涂鸦 Draw it Online
◆在线做 Do it by Penpa
