The even numbers a, b, c, and d that are not equal to each other and greater than 0 satisfy a+b+c+d=20, how many sets of even numbers (a, b, c, d) are there?
彼此不等且大于0的偶数a，b，c，d满足a+b+c+d=20，样的偶数组(a，b，c，d)共有多少组．
<gadget id="calculator">4 * 3 * 2 * 1</gadget>
<output>24</output>

<result>24</result>