1+2+3+4+5+6+7+8+9+...+99+100+99+98+...+4+3+2+1=how much.
1+2+3+4+5+6+7+8+9+…+99+100+99+98+…+4+3+2+1=多少．
<gadget id="calculator">1 + 100</gadget>
<output>101</output>

<gadget id="calculator">100 / 2</gadget>
<output>50</output>

<gadget id="calculator">101 * 50</gadget>
<output>5_050</output>

<gadget id="calculator">1 + 99</gadget>
<output>100</output>

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

<gadget id="calculator">100 * (99/2)</gadget>
<output>4_950</output>

<gadget id="calculator">5_050 + 4_950</gadget>
<output>10_000</output>

<result>10_000</result>