Xiaohua has a rectangular piece of colored paper with a length of 20 cm and a width of 15 cm. If he uses this colored paper to cut out the largest square, what is the perimeter of the square in centimeters?
小华有一张长20厘米、宽15厘米的长方形彩纸，如果他用这张彩纸剪一个最大的正方形，这个正方形的周长是多少厘米？
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<result>60</result>