Sum: 0.1+0.2+0.3+...+9.8+9.9+10+9.9+9.8+...0.3+0.2+0.1.
求和：0.1+0.2+0.3+…+9.8+9.9+10+9.9+9.8+…0.3+0.2+0.1．
<gadget id="calculator">0.1 + 9.9</gadget>
<output>10</output>

<gadget id="calculator">99 / 2</gadget>
<output>99/2 = around 49.5</output>

<gadget id="calculator">10 * (99/2) * 2</gadget>
<output>990</output>

<gadget id="calculator">990 + 10</gadget>
<output>1_000</output>

<result>1_000</result>