40 students want to cross the river by boat. There is only one boat at the ferry that can carry 4 people, but there is no boatman. They will all cross the river, at least how many times they will use this boat to cross the river.
40个同学要坐船过河，渡口处只有一只能载4人的小船，但是无船工．他们要全部渡过河去，至少要使用这只小船渡河多少次．
<gadget id="calculator">40 - 4</gadget>
<output>36</output>

<gadget id="calculator">36 / 3</gadget>
<output>12</output>

<gadget id="calculator">12 * 2</gadget>
<output>24</output>

<gadget id="calculator">24 + 1</gadget>
<output>25</output>

<result>25</result>