Put several apples into 9 drawers. No matter how you put them, you must ensure that there is always at least 4 apples in one drawer. So how many apples should there be at least?
把若干个苹果放进9个抽屉里，不管怎么放，要保证总有一个抽屉里至少放进4个苹果，那么至少应该有多少个苹果？
<gadget id="calculator">9 * 3</gadget>
<output>27</output>

<gadget id="calculator">27 + 1</gadget>
<output>28</output>

<result>28</result>