Teacher Wang took 18 students to participate in the summer camp. There is a shortcut to get to the accommodation quickly, but a river must be crossed. The boat by the river can carry 4 people at a time, and only Mr. Wang can row the boat. At least a few times, teachers and classmates can all cross the river?
王老师带着18名同学参加夏令营，有一条近路可以很快到达住宿的地方，但必须过一条河．河边的小船一次可以载4人，而只有王老师一个人会划船．至少几次，老师和同学们可以全部过河？
<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">18 / 3</gadget>
<output>6</output>

<result>6</result>