A four-digit number consisting of mutually distinct non-zero digits that sum to 13. How many such four-digit numbers are there?
一个四位数，它由和是13的互不相同的非零数字组成．则这样的四位数有多少个．
<gadget id="calculator">4 * 3 * 2 * 1</gadget>
<output>24</output>

<gadget id="calculator">24 + 24 + 24</gadget>
<output>72</output>

<result>72</result>