f(x) is a South Korean girl group formed by SM Entertainment: composed of four members in total: Victoria, Luna, Amber and Krystal, however, its original lineup also consisted of Sulli before she left the group before the release of their fourth, full-length album, 4 Walls in October 2015.

f(x) made their official debut on September 5, 2009 with the title track “La Cha Ta”, all before releasing their first full-length album, PINNOCHIO in 2011. Additionally, they are often cited as a musical inspiration for other Korean pop girl groups, mostly thanks to their critically-acclaimed album, July 2013’s Pink Tape, supported by the title track “Rum Pum Pum Pum”.