Wei Shuaishuai and 3 children meet in the park, if every two people shake hands once, how many times can they shake hands.
韦帅帅和3个小朋友在公园相遇，如果每两个人握一次手，他们可以握多少次手．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">3 / 2</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">4 * (3/2)</gadget>
<output>6</output>

<result>6</result>