1999*1999-2000*1998.
1999*1999-2000*1998．
<gadget id="calculator">1_999 - 1_998</gadget>
<output>1</output>

<gadget id="calculator">2_000 * 1</gadget>
<output>2_000</output>

<gadget id="calculator">1_999 * 1_999</gadget>
<output>3_996_001</output>

<gadget id="calculator">2_000 * 1_998</gadget>
<output>3_996_000</output>

<gadget id="calculator">3_996_001 - 3_996_000</gadget>
<output>1</output>

<gadget id="calculator">1_999 * 1</gadget>
<output>1_999</output>

<gadget id="calculator">2_000 - 1_999</gadget>
<output>1</output>

<result>1</result>