3, 4, 5, 6 are arranged into four digits without repeated numbers, arranged from small to large, what is the number 6345
由3，4，5，6排成没有重复数字的四位数，从小到大排起来，6345是第多少个
<gadget id="calculator">3 * 2 * 1 * 3</gadget>
<output>18</output>

<gadget id="calculator">18 + 1</gadget>
<output>19</output>

<result>19</result>