A rectangular piece of thick paper, 20 cm long and 15 cm wide. Cut it into the largest square, what is the perimeter of the square?
一张长方形厚纸，长20厘米，宽15厘米．把它剪成一个最大正方形，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>