Question: What is this South Korean-Chinese boy group formed by S.M. Entertainment in 2011 initially with several members and broke up a year later that released the song "Mama" in 2012?
Sentence (from "Exo (band)"): Formed by S.M. Entertainment in 2011, the group debuted in 2012 with twelve members separated into two subgroups, Exo-K (Suho, Baekhyun, Chanyeol, D.O., Kai, and Sehun) and Exo-M (Xiumin, Lay, Chen and former members Kris, Luhan and Tao ), performing music in Korean and Mandarin respectively.
Relevant evidence: Yes