How many line segments can be obtained by taking 7 subpoints (not including the endpoints) on a line segment.
在一条线段上取7个分点(不包括端点)，共可得到多少条线段．
<gadget id="calculator">7 + 2</gadget>
<output>9</output>

<gadget id="calculator">9 - 1</gadget>
<output>8</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">9 * 4</gadget>
<output>36</output>

<result>36</result>