A cylinder with a radius of 2 cm at the base and a square when its sides are expanded, what is the volume of the cylinder in cubic centimeters?
一个圆柱的底面半径为2厘米，侧面展开后正好是一个正方形，圆柱的体积是多少立方厘米．
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

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

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

<result>157.7536</result>