A section is 1 meter long. A piece of wood with a cross-sectional diameter of 20 cm floats horizontally on the surface of the water, and exactly half of it is exposed to the water, what is the area in square centimeters of the surface of this piece of wood in contact with the water?
一段长为1米．横截面直径为20厘米的木头横着浮在水面上，它正好一半露出水面，则这段木头与水接触面的面积是多少平方厘米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100 * 2</gadget>
<output>628</output>

<gadget id="calculator">3.14 * 20 * 1 * 100</gadget>
<output>6_280</output>

<gadget id="calculator">628 + 6_280</gadget>
<output>6_908</output>

<gadget id="calculator">6_908 / 2</gadget>
<output>3_454</output>

<result>3_454</result>