Can we do this if someone has reputation less than 50 this means he/she new to this community so when they try to ask some question, we can show a quick guide to them so that they can understand what is the proper way to ask a question and once the reputation becomes greater than 50 then no need to show quick guide.
Ask about this @admin if it can help 
I think @vivek_1998299 said that the TL was quite strict and that his solution using set failed. Try replacing it with a vector which is kept sorted. (Since deletion of lines was not supposed to happen afaik, the bad lines were just not inserted in first place.)