Time: 9:15pm IST
Solved A No idea B TLE C Not Read D -- Upsolve : Idea for A was exactly on point. can reduce time taken from 5 minutes to 4.
Got confused while solving B. Should've just written down math formulas instead of weird diagrams.
Was on right track for C i.e. greedy approach. Should've thought more about reducing time using hashmap.
Didn't read D since was preoccupied.
--- New Things to learn:
How to use lower_bound() Will read on C++ forums.
Euler totient functions: formula is easy but will watch youtube video for proof.
EDIT1 : Found link for proof. Time stamp for crux : 2:47
Euler totient proof
Pending :
Still need to solve D and understand logic. Read and try E
Cheers.