17 soldiers want to cross the river by boat, and there is only one boat at the ferry that can carry 5 people (no boatman). At least how many times will they all have to use this boat to cross the river? (one round trip each)
17个战士要坐船过河，渡口处只有一条能载5人的小船(无船夫)．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">17 - 5</gadget>
<output>12</output>

<gadget id="calculator">12 / 4</gadget>
<output>3</output>

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

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

<result>7</result>