<human>: Answer by taking a quote from the following article:

Westlife were an Irish pop vocal group, formed in Dublin in 1998 and disbanded in 2012. Originally signed by Simon Cowell and managed by Louis Walsh, the group's line-up consisted of Nicky Byrne, Kian Egan, Mark Feehily, Shane Filan and Brian McFadden, who was a member until his departure in 2004. Westlife sold over 50 million records worldwide, a total that included studio albums, singles, video releases, and compilation albums. The group accumulated 14 number-one singles in the United Kingdom.

The group released their eleventh UK No. 1 single, "Unbreakable" in 2002. Amidst rumours of a split, Westlife released their first greatest hits album in November that same year titled Unbreakable - The Greatest Hits Vol. 1, which zoomed all the way to No. 1 in the UK. The release was followed by the double A-side single "Tonight/Miss You Nights", which debuted at No. 3 in the UK. At this time, Because Films Inspire made a TV documentary titled "Wild Westlife", directed by Iain MacDonald and starred the group, featuring their daily life as musicians and their tour experiences. In 2003, Westlife went on their third world tour, The Greatest Hits Tour, shrugging off rumours of a split.  In September 2003, Westlife released "Hey Whatever", which peaked at No. 4 on the UK Charts. Their fourth studio album, Turnaround, was then released in November, earning the group another UK No. 1 album. "Mandy", a cover of the Barry Manilow hit, was released in November 2003. Their version won them their third Record of the Year award, in under five years. Their version of "Mandy" is also considered the single with the longest leap to the top (from No. 200 to No. 1) in UK music history. "Obvious" was released as the final single from the album, charting at #3.  On 9 March 2004, just three weeks prior to embarking on their fourth world tour, McFadden left the group to spend more time with his family and work on solo projects. On that day, a press conference was held where all the group's members were present, each giving emotional individual speeches. McFadden's final public performance as part of Westlife was at Newcastle upon Tyne's Powerhouse nightclub on 27 February 2004. He subsequently began a solo career, and reverted the spelling of his first name back to its original 'Brian'. He released his first solo single, "Real To Me", which entered the UK chart at No. 1 and soon after, he released his first solo album Irish Son under Sony Music. McFadden later released more singles, but only with moderate success.  Less than a month after McFadden's departure, the group kicked off their "Turnaround Tour". A live version of "Flying Without Wings" was released as an official UK download, earning them the first official UK Downloads number 1. CANNOTANSWER

what is unbreakable?
<bot>: The group released their eleventh UK No. 1 single, "Unbreakable" in 2002.