Calculation: 1+2+3+4+5+...+199=how much.
计算：1+2+3+4+5+…+199=多少．
<gadget id="calculator">1 + 199</gadget>
<output>200</output>

<gadget id="calculator">199 / 2</gadget>
<output>199/2 = around 99.5</output>

<gadget id="calculator">200 * (199/2)</gadget>
<output>19_900</output>

<result>19_900</result>