Calculation: 197*198-196*199=how much.
计算：197*198-196*199=多少．
<gadget id="calculator">197 * 198</gadget>
<output>39_006</output>

<gadget id="calculator">196 * 199</gadget>
<output>39_004</output>

<gadget id="calculator">39_006 - 39_004</gadget>
<output>2</output>

<result>2</result>