If a cylinder with a base diameter of 4 cm and a height of 8 cm is cut into two half cylinders along the base diameter, how much is the surface area increased?
把一个底面直径是4厘米，高8厘米的圆柱体沿底面直径切割成两个半圆柱，表面积增加了多少．
<gadget id="calculator">4 * 8 * 2</gadget>
<output>64</output>

<result>64</result>