Add 24 to 12 (the first operation), then subtract 20 (the second operation), add 24 (the third operation), and then subtract 20 (the fourth operation)... follow this rule , at least how many calculations can be done to get 2016.
将12加上24(第1次运算)，再减去20(第2次运算)，再加上24(第3次运算)，再减去20(第4次运算)…按此规律运算下去，最少经过多少次计算，能得到2016．
<gadget id="calculator">2_016 - 12 - 24</gadget>
<output>1_980</output>

<gadget id="calculator">24 - 20</gadget>
<output>4</output>

<gadget id="calculator">1_980 / 4</gadget>
<output>495</output>

<gadget id="calculator">495 * 2</gadget>
<output>990</output>

<gadget id="calculator">990 + 1</gadget>
<output>991</output>

<result>991</result>