If two squares with side lengths of 7 cm are used to form a rectangle, what is the perimeter of the rectangle in cm?
用两个边长是7厘米的正方形拼成一个长方形，这个长方形的周长是多少厘米．
<gadget id="calculator">7 + 7</gadget>
<output>14</output>

<gadget id="calculator">14 + 7</gadget>
<output>21</output>

<gadget id="calculator">21 * 2</gadget>
<output>42</output>

<result>42</result>