Use thin wooden strips to make a rectangular frame with a length of 12 cm and a width of 7 cm. How many centimeters of thin wooden strips are needed?
用细木条做一个长方形框，长12厘米，宽7厘米，需要细木条多少厘米．
<gadget id="calculator">12 + 7</gadget>
<output>19</output>

<gadget id="calculator">19 * 2</gadget>
<output>38</output>

<result>38</result>