15 students line up in a row facing the teacher, starting from the first one, report the number in the order of 1, 2, 3, 4, ..., the teacher asks, the students whose number is a multiple of 2 turn backwards, and then ask to report Students whose numbers are multiples of 3 turn backwards. How many people are facing the teacher at this time?
15个同学排成一排面向老师，从第一个开始，按1，2，3，4，…的顺序报数，老师要求，报的数是2的倍数的同学向后转，接着要求报的数是3的倍数的同学向后转，这时面向老师的有多少人？
<gadget id="calculator">15 - 7 - 4</gadget>
<output>4</output>

<gadget id="calculator">4 + 2</gadget>
<output>6</output>

<result>6</result>