It is known that the diameter of the base of a cylinder is 4 centimeters, and its side is exactly a square, then what is the volume of the cylinder in cubic centimeters.
已知一个圆柱的底面直径是4厘米，把它的侧面展开正好是一个正方形，那么这个圆柱的体积是多少立方厘米．
<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">12.56 * 12.56</gadget>
<output>157.7536</output>

<result>157.7536</result>