If 30 straight lines are drawn on a piece of white paper, how many points of intersection can appear at most?
在一张白纸上画30条直线，最多能出现多少个交点．
<gadget id="calculator">1 + 29</gadget>
<output>30</output>

<gadget id="calculator">29 / 2</gadget>
<output>29/2 = around 14.5</output>

<gadget id="calculator">30 * (29/2)</gadget>
<output>435</output>

<result>435</result>