Taken: Ah, Beh, Veh, Geh, Deh, Ye, Zhe, Ze, Ka, El, Em, En, O, Pe, Er, Es, U, Kha, Tse, Che, Yery, Myaki Znak, Eh, Yu, Apostrof. Not Taken: Yo, I, I Nyeskodovaya, Te, U Nyeskodovaya, Ef, Sha, Ya
Credit to jaren207 for the style