There are 4 Chinese teachers in the third grade, how many calls can be made with every two people.
三年级有4位语文老师，每两个人通一次电话，可以通多少次电话．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

<result>6</result>