Divide a circle with a radius of 2 decimeters into several equal parts and put together an approximate rectangle. The circumference of this rectangle is longer than the circumference of the circle by how many decimeters.
把一个半径是2分米的圆平均分成若干份，拼成一个近似的长方形，这个长方形的周长比圆的周长长多少分米．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<result>4</result>