How many line segments can be connected by 10 points on the same straight line?
同一条直线上的10个点可以连接多少条线段．
<gadget id="calculator">9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1</gadget>
<output>45</output>

<result>45</result>