28 soldiers have to cross the river by boat, and there is only one boat at the ferry that can carry 4 people (no boatman). They will all cross the river, at least how many times they will use this boat to cross the river. (one round trip each)
28名士兵要坐船过河，渡口处只有一条能载4人的小船(无船工)．他们要全部渡过河去，至少要使用这条小船渡河多少次．(往返各算一次)
<gadget id="calculator">28 - 4</gadget>
<output>24</output>

<gadget id="calculator">24 / 3</gadget>
<output>8</output>

<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<gadget id="calculator">16 + 1</gadget>
<output>17</output>

<result>17</result>