There are five friends at a party, if each person shakes hands with the rest of the people when they meet, how much is the total number of handshakes for the five people?
有五个朋友聚会，见面时如果每人都要和其余的人握一次手，那么5个人共握手多少
<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>