Question 16
2017 students arrange themselves in a single file. In the first round of counting, they number themselves $1,2,3,1,2,3,1,2,\ldots$ from left to right. In the second round, they number themselves $1,2,3,4,5,1,2,3,4,5,1,2,\ldots$ from right to left. Find the number of students whose difference between their numbers in the first and second rounds is 1.