SM Entertainment girl group f(x) are back and recently talked about their long awaited return.

f(x) spoke with the reporters backstage before a music show performance and shared their feelings regarding their comeback.  The quartet's recent single "4 Walls" was released on Oct. 27, and the members talked about their worries because the song is a different music genre than what fans are used to hearing from them.

"We all loved the song, but we were worried that its genre is different from our usual style," said the members, as reported by Soompi. "Thankfully, people seem to like it, so we are very grateful and happy."

While things have been slow-going since the group's last release in July 2014 with "Red Light," and the departure of Sulli (Choi Jin Ri) from the group on Aug. 7, the ladies of f(x) are happy to be back. "It has been such a long time, so we’re glad to be spending more time with each other," they told reporters.

"4 Walls" is the title track from the group's fourth full-length album of the same name. The lyrics are about falling in love unexpectedly, and the confusing feelings that follow.

f(x) will hold a solo concert in Seoul at the Olympic Stadium on January 30 and 31, 2016.