5 people play a table tennis match (single round robin), at least how many games should be played.
5人进行乒乓球比赛(单循环)，至少要赛多少场．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">4 * (5/2)</gadget>
<output>10</output>

<result>10</result>