Question: In what year was the South Korean boy group whose leader is Kang Seung-yoon formed?

Context articles: SF9 (band)
Kang Sung-hoon (singer)
Seventeen discography
We Broke Up
Baekho (singer)
Kang Seung-yoon
Victon
Love for a Thousand More
Winner (band)
Warrior (B.A.P song)

SF9 (Korean: 에스에프나인 ; shortened from Sensational Feeling 9) is a South Korean boy group formed by FNC Entertainment.
 SF9 is the company's first dance boy group to ever debut.
 SF9 debuted on October 5, 2016 with the release of their first single album "Feeling Sensation".
Kang Sung-hoon (hangul:강성훈, born February 22, 1980) is a South Korean singer from the 90's South Korean boy group Sechs Kies.
 Sung-hoon is the main vocalist of SechsKies and is referred to having the best singing voice of the group.
 After Sechskies had disbanded in 2000, Sung-hoon pursued a solo singing career, signed under Laful Entertainment at the time.
 His nickname Hoony is the title for his third album and his official fan club is called Hoony World.
This is the discography of South Korean boy group Seventeen.
 Seventeen (Hangul: 세븐틴), also stylized as SEVENTEEN or SVT, is a South Korean boy group formed by Pledis Entertainment in 2015.
 They have released one album and four EPs.
We Broke Up () is a South Korean web series based on the webtoon of the same name, starring Sandara Park and Kang Seung-yoon (both from YG Entertainment).
Kang Dong-ho (; born July 21, 1995), better known by the stage name Baekho (), is a South Korean singer-songwriter.
 He debuted in 2012 as a main vocalist of South Korean boy group NU’EST.
 He is also known for competing in the 2017 series "Produce 101 Season 2".
Kang Seung-yoon (born (1994--) 21, 1994 ), known as Seungyoon, is a South Korean singer-songwriter, record producer, actor, and leader of boy group Winner.
 In 2010, he participated in the reality television singing contest "Superstar K2" and finished in fourth place.
 In January 2011, he became a trainee under YG Entertainment and went on to debut as a solo artist in July 2013 and as the leader of Winner in October 2013.
Victon (Korean: 빅톤 ; stylized as VICTON, an acronym for Voice to New World), is a South Korean boy group formed by Plan A Entertainment in 2016.
 The group consists of Han Seung-woo, Kang Seung-sik, Heo Chan, Lim Se-jun, Do Han-se, Choi Byung-chan and Jung Su-bin, and made their debut on November 9, 2016 with the extended play "Voice to New World".
Love for a Thousand More (Hangul: 천년째 연애중 ; Hanja: 千年恋爱中 ; RR: "cheonnyeonjjae yeon-aejung " ) is a South Korea web series starring Kang Seung-yoon and .
 The drama is aired every Monday, Wednesday and Friday at 11:00 (KST) starting from December 5, 2016 till December 23, 2016 on Naver TV Cast (South Korea), YG Entertainment's YouTube Channel (International) and Miaopai (China).
Winner (Hangul: 위너), often stylized as WINNER, is a South Korean boy group formed in 2013 by YG Entertainment and debuted in 2014.
 It currently consists of four members, Jinwoo, Seunghoon, Mino and Seungyoon.
 Originally a five-piece group with Taehyun, who later departed from the group in November 2016.
"Warrior" (Korean: 워리어) is a song recorded by South Korean boy group B.A.P.
 It is released as a digital single on January 26, 2012 through TS Entertainment.
 The song served as B.A.P's debut single, the first from their self-titled debut album.
 "Warrior" was written and produced by Kang Ji-on and Kim Ki-bum, the same producers of Song Ji-eun's Going Crazy and Bang & Zelo's "Never Give Up".
 B.A.P's leader, Bang Yong-guk also participated in the song's production by co-writing "Warrior".
 The song's lyrics describes the injustice of the current society and how the protagonist's desire to end it.