作业中要求建一个MILP的模型，要求如下：
1. a set of exams,E
2. a single exam room that can seat C students
3. the number of students writing each exam. For exam i in the set E, Ci is the number of students writing exam i
4. a set of pairs of exams, P that are in conflict. That is, any exam pair(i,j) in the set P, cannot be scheduled at the same time.
The overall goal is to create an exam timetable with the minimum number of exam slots.
Q: Create a MILP model for the problem above.
