1*2+2*3+...+19*20.
1*2+2*3+…+19*20．
<gadget id="calculator">19 + 1</gadget>
<output>20</output>

<gadget id="calculator">2 * 19</gadget>
<output>38</output>

<gadget id="calculator">38 + 1</gadget>
<output>39</output>

<gadget id="calculator">39 / 6</gadget>
<output>13/2 = around 6.5</output>

<gadget id="calculator">19 * 20 * (13/2)</gadget>
<output>2_470</output>

<gadget id="calculator">1 + 19</gadget>
<output>20</output>

<gadget id="calculator">19 / 2</gadget>
<output>19/2 = around 9.5</output>

<gadget id="calculator">20 * (19/2)</gadget>
<output>190</output>

<gadget id="calculator">2_470 + 190</gadget>
<output>2_660</output>

<result>2_660</result>