Cut a rectangular piece of paper with a length of 20 cm and a width of 60 cm into small squares of equal size. If the area is the largest and there is no surplus, what is the side length of the square in cm?
把长20厘米，宽60厘米的长方形纸片剪成大小相等的小正方形，如面积最大而且没有剩余，正方形边长是多少厘米？
<gadget id="calculator">2 * 2 * 5</gadget>
<output>20</output>

<result>20</result>