UPD — seems the sieve function in my code caused some undefined behavior since it was getting out of bound, so I have got my answer. Thank you all who came forward to help. (I didn't even needed that function, it was left from the previous code, seems it was my unlucky day, atleast, got to learn something ;-;)

Why did I get runtime error for this code of mine in the competition?

link: https://mirror.codeforces.com/contest/1562/submission/127119400

While the same got accepted just after the competition

link: https://mirror.codeforces.com/contest/1562/submission/127129361

(exact same code)

PS- ;-; I am trying so hard to get better but these types of problem are so demotivating

MikeMirzayanov(edit-removed tag) please do help if possible ( I really don't want to be irritating ranting about my problem everywhere, but you see, this feels a big achievement to me, watching myself getting better everyday, and yes, ratings matter for me, rankings matter for me, it is kind of an adrenaline boost to me, so please help if possible ;-;)