How many three-digit numbers can be formed by using the four numbers 0, 5, 3, and 6 without repeating numbers.
用0、5、3、6四个数字组成没有重复数字的三位数，可以组成多少个．
<gadget id="calculator">3 * 3 * 2</gadget>
<output>18</output>

<result>18</result>