I would theorize that second used slavic language is not Ukrainian but Serbo-Croatian, at risk of getting hated by everybody mentioned.
It also has a rare property of coming with two alphabets - cyrillic and latin.
It also has a rare property of coming with two alphabets - cyrillic and latin.
And on top of that you must use the same criterion for the S-C language, not counting Slovenians, Albanians, Macedonians, etc who know the language but don't use it much anymore.