How to use nested ordered lists with different types?

Question

e.g a code for
A. Title 1
1. sub item1
2. sub item 2
B. Title 2
1. sub item 1
2. sub item 2
3. sub item 3
C......and so on

Answer 1

Try something like this :
https://code.sololearn.com/Wln68GA7FuBo/?ref=app