How many different points of intersection can there be at most for 2002 straight lines in the same plane?
同一平面内的2002条直线，最多可以有多少个不同的交点．
<gadget id="calculator">2_002 - 1</gadget>
<output>2_001</output>

<gadget id="calculator">2_002 * 2_001</gadget>
<output>4_006_002</output>

<gadget id="calculator">4_006_002 / 2</gadget>
<output>2_003_001</output>

<result>2_003_001</result>