If the length of a rectangle is increased by 2 centimeters and its width is increased by 1 centimeter, how many centimeters will its perimeter increase?
一个长方形的长增加2厘米，宽增加1厘米，它的周长增加多少厘米
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<result>6</result>