The side length of a square pond is 12 meters. One tree should be planted every 2 meters around the pond, and one tree should be planted at each of the four vertices. How many trees should be planted in total?
一个正方形池塘的边长是12米，要在池塘四周每隔2米栽一棵树，四个顶点各栽一颗，一共要栽多少颗树．
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<gadget id="calculator">7 * 4</gadget>
<output>28</output>

<gadget id="calculator">28 - 4</gadget>
<output>24</output>

<result>24</result>