A cylinder with a base diameter of 4 decimeters is a square when its sides are expanded. What is the volume of this cylinder in cubic decimeters?
一个圆柱体底面直径是4分米，侧面展开后是正方形．这个圆柱的体积是多少立方分米？
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">3.14 * 4 * 12.56</gadget>
<output>157.7536</output>

<result>157.7536</result>