Calculation: 50+49-48-47+46+45-44-43+...-4-3+2+1.
计算：50+49-48-47+46+45-44-43+…-4-3+2+1．
<gadget id="calculator">2 * 25</gadget>
<output>50</output>

<gadget id="calculator">50 + 1</gadget>
<output>51</output>

<result>51</result>