See [https://www.math.mcgill.ca/~darmon/courses/18-19/gs/serre-mcgill.pdf](https://www.math.mcgill.ca/~darmon/courses/18-19/gs/serre-mcgill.pdf)

- Try exercises
    - [x]  i.5, abcd
    - [ ]  Exc 1-2
    - [ ]  ii.2
    - [ ]  ii.5