f(x) prove that they are stronger than ever with their comeback with 4 Walls.

At today's M!Countdown, the revamped f(x), who made their comeback as four-member group nab their first win. Overwhelmed how everything is turning alright, Luna and Krystal weren't able to contain their emotions and started shedding tears while hugging each other.

Meanwhile, leader Victoria gave her thank you speech especially for their fans who have been always with them. f(x) was up against Lim Chang Jung for this week.  Congratulations f(x)!