There are 15 students who want to cross the river, there is only one boat, and only 3 people can take each time, at least how many times will it take to cross the river.
有15名学生要过河，只有一条船，每次只坐3人，至少要多少次才能全部过河．
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 + 1</gadget>
<output>7</output>

<result>7</result>