Question: What number of studio album release did U2's Innocence + Experience Tour support?

full_context: Document 1: The Joshua Tree Tour 2017: The Joshua Tree Tour 2017 is an ongoing worldwide concert tour by rock band U2 commemorating the 30th anniversary of their 1987 album, "The Joshua Tree". The tour is visiting stadiums in 2017 across four legs: North America from May to July and in September, Europe from July to August, and Latin America in October. It began on 12 May 2017 in Vancouver, Canada. The band intends to play "The Joshua Tree" in its entirety on each date of the tour, marking the first live performances of the song "Red Hill Mining Town". It is the first time the group is touring in promotion of an album from their back catalogue, rather than a new release. As part of the tour, U2 headlined the Bonnaroo Music Festival in Manchester, Tennessee, in June.
Document 2: Songs of Experience (U2 album): Songs of Experience is the upcoming fourteenth studio album by Irish rock band U2. It will be released on 1 December 2017. The album is intended to be a companion piece to U2's previous record, "Songs of Innocence" (2014). Whereas its predecessor explored the group members' adolescence in Ireland in the 1970s, "Songs of Experience" thematically will be a collection of letters written by lead vocalist Bono to people and places closest to his heart. The personal nature of the lyrics reflects a "brush with mortality" that he had during the album's recording. The band collaborated with a variety of producers for the record, including Steve Lillywhite, Ryan Tedder, Jacknife Lee, Jolyon Thomas, and Andy Barlow.
Document 3: Songs of Innocence (U2 album): Songs of Innocence is the thirteenth studio album by Irish rock band U2. Released on 9 September 2014, it was produced by Danger Mouse, with additional production from Paul Epworth, Ryan Tedder, Declan Gaffney, and Flood. The album was announced at an Apple Inc. product launch event and released the same day to all iTunes Store customers at no cost. It was exclusive to iTunes, iTunes Radio, and Beats Music until 13 October 2014, when it received a physical release on Island and Interscope Records. The digital release made the record available to over 500 million iTunes customers, for what Apple CEO Tim Cook marketed as "the largest album release of all time".
Document 4: On the Road Again Tour: The On the Road Again Tour was the fourth headlining concert tour by English-Irish boy band One Direction. It promoted the band's fourth studio album, "Four". The tour began on 7 February 2015 in Sydney, Australia and ended on 31 October 2015 in Sheffield, England. The majority of the tour venues were sold out, bringing in revenue of $208 million from 80 shows total.
Document 5: U2 360° Tour: The U2 360° Tour was a worldwide concert tour by rock band U2. Launched in support of the group's 2009 album "No Line on the Horizon", the tour visited stadiums from 2009 through 2011. The concerts featured the band playing "in the round" on a circular stage, allowing the audience to surround them on all sides. To accommodate the stage configuration, a large four-legged structure nicknamed "The Claw" was built above the stage, with the sound system and a cylindrical, expanding video screen on top of it. At 164 ft tall, it was the largest stage ever constructed. U2 claimed that the tour would be "the first time a band has toured in stadiums with such a unique and original structure."
Document 6: Innocence + Experience: Live in Paris: Innocence + Experience: Live in Paris (stylised as iNNOCENCE + eXPERIENCE: Live in Paris) is a 2016 concert film by Irish rock band U2. It was shot on 7 December 2015 at AccorHotels Arena in Paris, France, during the final date of the band's Innocence + Experience Tour. The concert aired on American television network HBO the same day as the show, and was later released worldwide on home video on DVD, Blu-ray, and via digital download on 10 June 2016.
Document 7: The Joshua Tree: The Joshua Tree is the fifth studio album by Irish rock band U2. It was produced by Daniel Lanois and Brian Eno, and was released on 9 March 1987 on Island Records. In contrast to the ambient experimentation of their 1984 release, "The Unforgettable Fire", the band aimed for a harder-hitting sound within the limitation of conventional song structures on "The Joshua Tree". The album is influenced by American and Irish roots music, and through sociopolitically conscious lyrics embellished with spiritual imagery, it contrasts the group's antipathy for the "real America" with their fascination with the "mythical America".
Document 8: Zoo TV Tour: The Zoo TV Tour (also written as ZooTV, ZOO TV or ZOOTV) was a worldwide concert tour by rock band U2. Staged in support of their 1991 album "Achtung Baby", the tour visited arenas and stadiums from 1992 to 1993. To mirror the new musical direction that the group took with "Achtung Baby", the tour was intended to deviate from their past and confound expectations of the band. In contrast to U2's austere stage setups from previous tours, the Zoo TV Tour was an elaborately staged multimedia event. It satirised television and media oversaturation by attempting to instill "sensory overload" in its audience. To escape their reputation for being earnest and overly serious, U2 embraced a more lighthearted and self-deprecating image on tour. Zoo TV and "Achtung Baby" were central to the group's 1990s reinvention.
Document 9: The Miracle (Of Joey Ramone): "The Miracle (Of Joey Ramone)" is a song by Irish rock band U2. It is the opening track from their thirteenth studio album, "Songs of Innocence", and was released as its lead single. It was produced by Danger Mouse, Paul Epworth, and Ryan Tedder. It was first unveiled by the band at an Apple Inc. product launch event on 9 September 2014, coinciding with an announcement that "Songs of Innocence" would be released digitally to iTunes Store customers free of charge. The song's title refers to American musician Joey Ramone, lead singer of influential punk rock band, the Ramones.
Document 10: Achtung Baby: Achtung Baby ( ) is the seventh studio album by Irish rock band U2. It was produced by Daniel Lanois and Brian Eno, and was released on 18 November 1991 on Island Records. Stung by criticism of their 1988 release, "Rattle and Hum", U2 shifted their musical direction to incorporate influences from alternative rock, industrial music, and electronic dance music into their sound. Thematically, "Achtung Baby" is darker, more introspective, and at times more flippant than their previous work. The album and the subsequent multimedia-intensive Zoo TV Tour were central to the group's 1990s reinvention, by which they abandoned their earnest public image for a more lighthearted and self-deprecating one.
Document 11: Innocence + Experience Tour: The Innocence + Experience Tour (styled as iNNOCENCE + eXPERIENCE Tour) was a worldwide concert tour by rock band U2. Staged in support of the band's 2014 album "Songs of Innocence", the tour visited arenas throughout 2015. It was U2's first time playing arenas since 2005–2006 on their Vertigo Tour. Comprising two legs and 76 concerts, the Innocence + Experience Tour began on 14 May 2015 in Vancouver, Canada. It visited North America from May through July, and Europe from September through December. Shows were predominantly booked in pairs for each market.
Document 12: All That You Can't Leave Behind: All That You Can't Leave Behind is the tenth studio album by Irish rock band U2. It was produced by Brian Eno and Daniel Lanois, and was released on 30 October 2000 on Island Records in the United Kingdom and Interscope Records in the United States. Following the mixed reception to their 1997 album, "Pop", "All That You Can't Leave Behind" represented a return to a more mainstream sound for the band after they experimented with alternative rock and dance music in the 1990s. At the time of the album's release, U2 said on several occasions that they were "reapplying for the job ... [of] the best band in the world". U2 brought back Eno and Lanois, who had produced three of the band's previous albums. The album was originally named "U2000", which had been a working title for their PopMart Tour.
Document 13: Vertigo Tour: The Vertigo Tour was a worldwide concert tour by the Irish rock band U2. Staged in support of the group's 2004 album "How to Dismantle an Atomic Bomb", the tour visited arenas and stadiums from 2005 through 2006. The Vertigo Tour consisted of five legs that alternated between indoor arena shows in North America and outdoor stadium shows internationally. Much like the previous Elevation Tour, the indoor portion of the Vertigo Tour featured a stripped-down, intimate stage design. Protruding from the main stage was an ellipse-shaped catwalk that encapsulated a small number of fans.
Document 14: Elevation Tour: The Elevation Tour was a worldwide concert tour by the Irish rock band U2. Launched in support of the group's 2000 album "All That You Can't Leave Behind", the tour visited arenas in 2001. After the band's previous two extravagant stadium tours, Zoo TV and PopMart, the Elevation Tour returned the band to indoor arenas with a much more stripped-down, intimate stage design. A heart-shaped B-stage extended from the main stage, while encapsulating many of the fans.
Document 15: U2 discography: The discography of Irish rock band U2 consists of thirteen studio albums, one live album, three compilation albums, sixty-seven singles, and eight extended plays (EPs). The band formed at Mount Temple Comprehensive School in 1976 as teenagers. In 1979, the group issued their first release, the EP "U2-3", which sold well in Ireland. The following year, the group signed to Island Records and released their debut album, "Boy". It reached number 52 in the UK and number 63 in the US. They followed it up with the release of "October" (1981) and "War" (1983). "War" was a commercial success, becoming the band's first number-one album in the UK while reaching number 12 in the US. The album yielded the singles "Sunday Bloody Sunday" and "New Year's Day" and have since become among the band's most popular songs. On the subsequent War Tour, the group recorded the live album "Under a Blood Red Sky" and concert film "", both of which sold well and helped establish them globally as a live act.
ground_truth: thirteenth