Teacher Liu made a cylindrical pen holder. The diameter of the bottom of the pen holder is 10cm and the height is 20cm. If you paste colored paper on the side and bottom of the pen holder, how much colored paper should you use at least?
刘老师制作了一个圆柱形笔筒，笔筒的底面直径是10cm，高20cm，如果在笔筒的侧面和底面贴上彩纸，至少要用多少彩纸？
<gadget id="calculator">3.14 * 10 * 20</gadget>
<output>628</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<gadget id="calculator">628 + 78.5</gadget>
<output>706.5</output>

<result>706.5</result>