Calculation: 1*2+2*3+3*4+...+18*19+19*20.
计算：1*2+2*3+3*4+…+18*19+19*20．
<gadget id="calculator">9 + 1</gadget>
<output>10</output>

<gadget id="calculator">2 * 9</gadget>
<output>18</output>

<gadget id="calculator">18 + 1</gadget>
<output>19</output>

<gadget id="calculator">19 / 6</gadget>
<output>19/6 = around 3.166667</output>

<gadget id="calculator">8 * 9 * 10 * (19/6)</gadget>
<output>2_280</output>

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

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">2 + 6 + 12</gadget>
<output>20</output>

<gadget id="calculator">19 * 20</gadget>
<output>380</output>

<gadget id="calculator">2_280 + 380</gadget>
<output>2_660</output>

<result>2_660</result>