21 expedition members cross a small river, and there is only one boat that can carry 5 people. How many times do all team members need to cross the river at least?
21名探险队员过一条小河，只有一条可乘5人的小船，全体队员渡到河对岸至少需要多少次．
<gadget id="calculator">21 - 1</gadget>
<output>20</output>

<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<result>5</result>