Xiaohai regards (16+□)*20 as 16+□*20, so how much is the difference between his calculated result and the correct result.
小海把(16+□)*20看成了16+□*20，那么他算出得结果与正确的结果相差多少．
<gadget id="calculator">320 - 16</gadget>
<output>304</output>

<result>304</result>