There are 8 points at different positions on a circle, how many lines can be connected with these 8 points as endpoints?
一个圆上，在不同位置有8个点，以这8个点为端点，一共可以连成多少条线．
<gadget id="calculator">7 + 6 + 5 + 4 + 3 + 2 + 1</gadget>
<output>28</output>

<result>28</result>