New Year's Day is coming, 4 children sent each other a holiday greeting card, how many cards did they send in total?
元旦快到了，4个小朋友互相寄一张节日贺卡，一共寄了多少张？
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<result>12</result>