Xiaoqing only remembers that Lingling's phone number is: 870435□□, and also remembers that the largest number is 9, each number is not repeated, how many times does Xiaoqing have to try to dial Lingling's number at most.
小青只记得灵灵的电话号码是：870435□□，还记得最大的数字是9，各个数字又不重复，拨通灵灵电话，小青最多需试打多少次．
<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<result>12</result>