Nail it into a rectangular frame with thin wooden strips. The length is 13 cm and the width is 7 cm. If it is drawn into a parallelogram, what is its perimeter in cm?
用细木条钉成一个长方形框．长13厘米，宽7厘米，如果把它拉成一个平行四边形，它的周长是多少厘米．
<gadget id="calculator">13 + 7</gadget>
<output>20</output>

<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<result>40</result>