A piece of rectangular paper is 28 cm long and 15 cm wide. Cut out the largest square first, and then cut out the largest square from the rest of the paper. What is the perimeter of the remaining rectangle in cm?
一张长方形的纸，长是28厘米，宽是15厘米，先剪下一个最大的正方形，再从余下的纸片中，剪下一个最大的正方形，最后余下的长方形周长是多少厘米．
<gadget id="calculator">28 - 15</gadget>
<output>13</output>

<gadget id="calculator">15 - 13</gadget>
<output>2</output>

<gadget id="calculator">13 + 2</gadget>
<output>15</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<result>30</result>