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:

1. How to use lower_bound() Will read on C++ forums.

2. 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

EDIT2: Found link for lower_bound() Lower_bound reference

---- Pending :

Read and try E

Cheers.