There are 30 class reunions, and everyone shakes hands with everyone else when they meet, how many handshakes did they have in total?
有30个同学聚会，见面时每人都和其他人握一次手，那么总共握了多少次手？
<gadget id="calculator">30 - 1</gadget>
<output>29</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>