TLDR somehow codeforces judge is working way slower than oj.uz

Hello codeforces! As the IOI is coming closer and closer, I started upsolving some of the IOI tasks. For many of you, i guess, it's not a secret that there is an IOI archive on codeforces.

Sadly I faced this problem (already at least twice): Same code running on oj.uz and on codeforces gets difent score. Surprisingly, smaller one belongs to cf.

As I thought, codeforces judge should be faster, no? Instead I have:

Problem IOI18_seats, TL on codeforces is 3 seconds, which should be enough for 2 seconds taking it to run on oj.uz

Another example: