Trees were planted every 4 meters between the cafeteria and the dormitory, and a total of 6 trees were planted. Now it is changed to plant a tree every 2 meters, how many trees are needed?
食堂和宿舍之间每隔4米栽树，共栽了6棵树．现改成每隔2米栽一棵树，需要多少棵树？
<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">14 - 1</gadget>
<output>13</output>

<result>13</result>