When a car picking up students left the garage, there was only one driver and one student on board. Later, students got on the car at three stations, and no students got off the car along the way. At each station after the first, twice as many students board as at the previous station. When the car arrives at the school, the number of students in the car can only be how many
一辆接送学生的汽车，离开车库时，车上只有一个司机和一个学生，后来共有3个车站有学生上车，一路上没有学生下车．在第一个车站以后的每一个车站，上车的学生数是在前一站上车的学生数的两倍．当汽车到达学校的时候，车上的学生人数只可能是多少
<gadget id="calculator">7 * 6</gadget>
<output>42</output>

<gadget id="calculator">42 + 1</gadget>
<output>43</output>

<result>43</result>