Not so easy maths

#1

whats the error in my codes

#2

@drishti307 Your code runs in O(n) here n is of the order 18 so this will not work.
This question is based on the principal of inclusion and exclusion.
https://www.youtube.com/watch?v=tMRZ6gqFYdg
Here is a video of Prateek sir discussing the principle of inclusion and exclusion using same kind of problem
If this resolves your doubt mark it resolved.

#3

thank you very much for the help