Exam Cheating

Ram and Shyam are sitting next to each other, hoping to cheat on an exam. However, the examination board has prepared $p$ different sets of questions (numbered $0$ through $p-1$), which will be distributed to the students in the following way: - The students are assigned roll numbers — pairwise distinct positive integers. - If a student's roll number is $r$, this student gets the $((r-1)\%p)$-th