If the radii of two circles differ by 1 centimeter, what is the difference in circumference of the two circles in centimeters?
已知两个圆的半径相差1厘米，则这两个圆的周长相差多少厘米．
<gadget id="calculator">3.14 * 2 * 2</gadget>
<output>12.56</output>

<gadget id="calculator">3.14 * 2 * 1</gadget>
<output>6.28</output>

<gadget id="calculator">12.56 - 6.28</gadget>
<output>6.28</output>

<result>6.28</result>