During the Spring Festival, 4 children agree to make a phone call every two children, how many times will they call in total?
春节期间，4个小朋友约定每两个小朋友通电话一次，他们一共要通多少次电话．
<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>