If the lengths of two adjacent sides of a parallelogram are 12 cm and 4 cm respectively, what is its perimeter?
平行四边形相邻两边长分别是12厘米和4厘米，它的周长是多少．
<gadget id="calculator">12 + 4</gadget>
<output>16</output>

<gadget id="calculator">16 * 2</gadget>
<output>32</output>

<result>32</result>