4 students queued up to receive the water, and Xiaohong was the first in line. It took her 2 minutes to receive the water. How many minutes did the students behind her wait in total?
4个同学排队接水，小红排第一位，她接水花了2分钟，她后面的同学一共等待了多少分钟．
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

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

<result>6</result>