How many three-digit numbers can be formed with the four numbers 0, 4, 6, and 7 without repeating numbers?
用0、4、6、7这四个数字可以组成多少个没有重复数字的三位数．
<gadget id="calculator">3 * 3 * 2 * 1</gadget>
<output>18</output>

<result>18</result>