Question: When was the group in which South Korean rapper and singer Bobby debuted formed?
Context: Lee Ye-ji (born August 26, 1994), better known by her stage name Yezi, is a South Korean rapper and singer.  She debuted as a member of South Korean girl group Fiestar in 2012.  Yezi was a semi-finalist on "Unpretty Rapstar 2" in 2015, during which she released several singles.  Her debut solo maxi single, "Foresight Dream", was released on January 28, 2016. Ravi is a South Korean rapper, songwriter and producer, signed under Jellyfish Entertainment.  He began his career as a rapper in 2012 in the South Korean boy group VIXX, and later formed VIXX's first sub-unit VIXX LR with band mate Leo in 2015.  Ravi's songwriting career began with his participation in co-writing VIXX's debut single "Super Hero".  As of November 2016 with the release of "VIXX 2016 Conception Ker", Ravi has contributed to the writing and composing of over 46 songs recorded by VIXX.  Ravi is widely known for his participation of composing and songwriting rap portions for the group as well as lyrics and music. Jeon Ji-yoon (born October 15, 1990), better known mononymously as Jiyoon or by her stage name Jenyer, is a South Korean rapper, singer-songwriter and actress.  She was previously a member of South Korean girl group 4Minute and its sub-group 2Yoon.  She debuted as a solo artist on November 2, 2016, under the stage name Jenyer, with the release of her debut digital single, "I Do". The Gwiyomi Song, or Kwiyomi Song (귀요미 송), is a K-pop single by South Korean singer Hari and was released on February 18, 2013.  It was inspired by a gesture from South Korean rapper Jung Ilhoon of boy group BtoB.  The gesture is called 'Gwiyomi Player', that was popularized by South Korean variety show "Weekly Idol" through a segment called "The Aegyo Battle" (Battle of Cuteness) following Ilhoon's guest appearance on the show in October 2012.  The song went on to be a viral success and an Internet meme after Korean Media outlet "Sports Seoul" uploaded a clip of Hari performing the gestures and singing the song.  This video has since inspired many Asian netizens to upload their own versions onto the internet. iKon (Hangul: 아이콘 ), stylized as iKON, is a South Korean boy band formed in 2015 by YG Entertainment.  The group was first introduced in the reality survival program "WIN: Who is Next" as "Team B." After that, Team B went on to appear in the 2014 reality survival program "Mix & Match", which determined the final seven-member lineup of iKon: B.I, Bobby, Jay, Ju-ne, Song, DK and Chan. Choi Seung-hyun (; born November 4, 1987), better known by his stage name T.O.P, is a South Korean rapper, singer, songwriter, record producer and actor.  T.O.P rose to fame in the mid-2000s as one of two rappers in the South Korean boy band Big Bang.  Released under YG Entertainment, the group became one of the best-selling groups of all-time in Asia and one of the best-selling boy bands in the world.  In 2010, while the group was on hiatus, T.O.P and G-Dragon formed a duo to record and release the number-one collaboration album, "GD & TOP".  As a solo rapper, he has released two digital singles, "Turn It Up" (2010) and "Doom Dada" (2013), which peaked at number two and four, respectively, on the Gaon Digital Chart. South Korean rapper and singer Bobby debuted as a member of the South Korean hip hop group iKON.  His discography as a solo artist began in 2014.  His self-produced debut album "Love and Fall" was released in 2017.  As a member of the duo MOBB with Mino, he has released one collaboration album as well as several other singles and featured singles. Ok Taec-yeon (; born December 27, 1988), known mononymously as Taecyeon, is a South Korean rapper, singer, songwriter, actor and entrepreneur.  He is the main rapper of the South Korean boy group 2PM. Lim Sung-bin (Hangul: 임성빈; born September 12, 1987), better known by the stage name Beenzino (Hangul: 빈지노), is a South Korean rapper currently signed under Illionaire Records.  His stage name is a play on that of Boston rapper Benzino, combined with "빈" (pronounced "been") from his birth name.  Beenzino made his first official public appearance at Dok2's Hustle Real Hard Concert on June 5, 2011 and has since released three solo albums, as well as other works in collaboration with hip hop producers Primary and Shimmy Twice, and as the duo Hot Clip with South Korean rapper Beatbox DG.  He is noted for his melodic style of rapping. Kim Won-sik (Hangul: 김원식 , born February 15, 1993) better known by his stage name Ravi (Hangul: 라비 ), is a South Korean rapper, singer-songwriter, producer, signed under Jellyfish Entertainment.  He is a member of the South Korean boy group VIXX and VIXX sub-unit VIXX LR.  He debuted as a solo artist on January 9, 2017, with the release of his debut mini album "R.EAL1ZE".
Answer: 2015