Submission in C++20 — WA

Submission in C++17 — AC

The same code is giving different output in different version of C++, but what is the reason causing it?

I started my cp journey in Feb of 2022, initially I thought of dsa as cp and used to do leetcode a lot, then I slowly got know about codeforces and codechef in mid February. damn all the problems looks so easy but were so difficult to do it while coding, so I decided to study algorithms then try it again, so rest of feb I devoted to only studying them, but when I came back in March damn still couldn't do any hardly. I thought to myself I am not meant for it, should leave cp and try dev.

But something back of my mind said to try again as a game , just a win or lose will add to my experience, so I kept on trying problems and did many problems , eventually I got the hang of it and was able to solve some, and at that time it became fun for me, I started thinking of it as a game, which helps me a lot cause I could compare it with CSGO (only game I used to play).

So I knew I had to put in a lot of efforts even to see a slight progress, and I am right now in the process of doing so , solving problems above my caliber and giving contest and not caring about the rating.

I am thinking of participating in only Div 2 contests and try to solve consistently doing A and B, s it a good idea? My rating right now is 927 and I have given about 4 contests