Use several rectangular pieces of paper with a length of 20 cm and a width of 16 cm to assemble a square. What is the minimum side length of the square?
用若干个长20厘米，宽16厘米的长方形纸拼正方形，正方形的边长最小是多少？
<gadget id="calculator">2 * 2 * 2 * 2 * 5</gadget>
<output>80</output>

<result>80</result>