I'm a member of codeforces for a while now, and I'm familiar with format of contests, website interface etc. I have seen this post about tomorrow's SRM on topcoder and I've decided to participate in. Do I need to register for the contest as in codeforces' rounds? And it also seemed like I can't use my own editor on arena. Do I have to use the coding area to code the solution? Is there an option or workaround not to use its built-in editor? I'm also curios which one's (topcoder or codeforces) type of problems more similar to IOI?