When n=8, how much should be filled in □ of "4n+□=63".
当n=8时，"4n+□=63"的□中应填多少．
<gadget id="calculator">4 * 8</gadget>
<output>32</output>

<gadget id="calculator">63 - 32</gadget>
<output>31</output>

<result>31</result>