The karaoke hall has a circular performance stage with a circumference of 31.4 meters. Now the radius is widened by 1 meter, how many square meters is increased from the original area?
歌厅有一个圆形表演台，周长31.4米．现在半径加宽1米，比原来的面积增加多少平方米？
<gadget id="calculator">3.14 * 225</gadget>
<output>706.5</output>

<gadget id="calculator">31.4 / 3.14 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<gadget id="calculator">706.5 - 78.5</gadget>
<output>628</output>

<result>628</result>