this is common thing that happened to me when i solve a problem and i want to submit it then i got WA because of i forgot to comment my testing file input... Now i saw that someone use this in main - - #ifdef NEREVAR_PROJECT - freopen("input.txt", "r", stdin); - freopen("output.txt", "w", stdout); - #endif

but i don't understand that many people use many different thing at the position "NEREVAR_PROJECT" .. then i am trying to copy that and use but it's not work in my text editor . plz explain me what is it and what it means and what it does...and how it use... thanx in advance