If the lengths of two adjacent sides of a parallelogram are 6 cm and 7 cm, what is the perimeter of the parallelogram in cm?
平行四边形相邻的两条边长分别是6厘米和7厘米，这个平行四边形的周长是多少厘米．
<gadget id="calculator">6 + 7</gadget>
<output>13</output>

<gadget id="calculator">13 * 2</gadget>
<output>26</output>

<result>26</result>