Definition: x☆=x*(x+1), x☆☆=x☆*(x☆+1), then 1☆☆☆☆=how much.
定义：x☆=x*(x+1)，x☆☆=x☆*(x☆+1)，那么1☆☆☆☆=多少．
<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">1 * 2</gadget>
<output>2</output>

<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">1 * 2 * 3</gadget>
<output>6</output>

<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<gadget id="calculator">6 * 7</gadget>
<output>42</output>

<gadget id="calculator">42 + 1</gadget>
<output>43</output>

<gadget id="calculator">6 * 7 * 43</gadget>
<output>1_806</output>

<result>1_806</result>