A piece of rectangular paper is 28 cm long and 15 cm wide. After cutting out the largest square, what is the perimeter of the remaining rectangular paper in cm?
一张长方形纸，长28厘米，宽15厘米，剪下一个最大的正方形后，余下的长方形纸的周长是多少厘米．
<gadget id="calculator">28 - 15</gadget>
<output>13</output>

<gadget id="calculator">15 + 13</gadget>
<output>28</output>

<gadget id="calculator">28 * 2</gadget>
<output>56</output>

<result>56</result>