Does anyone know if SGU online judge(http://acm.sgu.ru/) is down permanently? Or may be website address changed?

Hi Everyone,

I'm a newbie here.I just started solving Div 2 A problems. I solved the following problem using a brute force approach. http://codeforces.me/problemset/problem/194/A

I was looking at the editorial here — http://codeforces.me/blog/entry/4673 I don't understand the logic behind "3n-k" being used.

Can anyone please help?