Question: Which American singer-songwriter that had 15 number one singles in 2015 helped Shakira write Medicine?
Context: Kill the Lights is the fifth studio album by American country music artist Luke Bryan.  It was released on August 7, 2015, by Capitol Nashville.  The album's lead single, "Kick the Dust Up", was released to country radio on May 19, 2015. " Strip It Down" was released as the second single from the album on August 4, 2015.  The album's third single, "Home Alone Tonight", was released to country radio on November 23, 2015.  The album's fourth single, "Huntin', Fishin' and Lovin' Every Day" released to country radio on March 14, 2016.  The album's fifth single, "Move" released to country radio on July 25, 2016.  All five singles reached number one on the "Billboard" Country Airplay chart, making Bryan the first country music artist ever to have five number one singles from two albums apiece.  In November 2016, the album's sixth and final single, "Fast", was sent to country radio.  With "Fast" also reaching number one in April 2017, Bryan became the first artist in the chart's history to achieve six number one singles from one album. "Medicine" is a song recorded by Colombian singer and songwriter Shakira from her tenth studio album "Shakira" (2014).  Featuring guest vocals from American country music singer Blake Shelton, the song was performed on the 49th Annual Academy of Country Music Awards on April 6, 2014, and spent one week on the country charts at number 57 from unsolicited airplay.  The song was written by Shakira alongside Mark Bright and Hillary Lindsey, while the production was handled by Shakira and busbee. Summer Forever is the sixth studio album by American country music singer Billy Currington.  It was released on June 2, 2015 via Mercury Nashville.  The album includes the number one singles "Don't It", "It Don't Hurt Like It Used To" and "Do I Make You Wanna".  This is Currington's fifth consecutive album to contain at least two number one singles and his first album to have three singles at the top of the charts. Hillary Lindsey is an American singer-songwriter.  She has written songs with or for several popular artists including Michelle Branch, Faith Hill, Martina McBride, Shakira, Lady Antebellum, Gary Allan, Sara Evans, Carrie Underwood, Kellie Pickler, Bon Jovi, Taylor Swift, Lady Gaga, Tim McGraw and Luke Bryan.  Lindsey won a Grammy Award for Best Country Song for Carrie Underwood's "Jesus, Take the Wheel".  In 2011, Lindsey received an Academy Award nomination for "Coming Home", recorded by Gwyneth Paltrow for the soundtrack of "Country Strong", in the Best Original Song category.  "Coming Home" also received a Golden Globe that same year for Best Original Song along with "There's A Place For Us", making Lindsey a double nominee in 2011.  As of 2015, she has had 15 number one singles as a writer. "Who's That Girl" is an up-tempo electro R&B song performed by Australian singer-songwriter Guy Sebastian which features American rapper Eve.  It was written by Sebastian, with Eve writing and performing the rap.  Sebastian co-produced the song with Andre Harris.  Released as a digital download on 5 November 2010, it was the only single released in Australia from Sebastian's retrospective album "Twenty Ten".  "Who's That Girl" reached number one on the ARIA Singles Chart, Sebastian's fifth of six number one singles in Australia and Eve's first.  It was also Sebastian's seventh of 12 top ten singles on the Australian charts.  It reached 5× platinum certification in 2014.  "Who's That Girl" was shortlisted for the 2011 APRA Song of the Year and won the APRA Urban Work of the Year.  Sebastian received ARIA Award nominations for Single of the Year and Best Pop Release and won the Highest Selling Single ARIA.  He was also nominated as "Most Popular Australian Artist".  "Who's That Girl" also reached number one and platinum certification in New Zealand, Sebastian's second number one single there. <ref name="Latest Gold/Platinum Singles">Latest Gold/Platinum Singles.  RadioScope New Zealand.  Archived from the original on 24 July 2011.  Retrieved 15 January 2012. </ref> Dwight Yoakam is an American country music singer-songwriter.  Since his debut single, "Honky Tonk Man" in 1986, he has released 46 singles, including two "Billboard" Hot Country Songs number one singles, as well as 4 number ones in Canada.  In addition to having two number one singles in the United States, Yoakam also has thirteen Top 10 singles on the country chart. Boyzone are an Irish boy band.  Their most famous line-up was composed of Keith Duffy, Stephen Gately, Mikey Graham, Ronan Keating, and Shane Lynch.  Boyzone have had 21 singles in the top 40 UK charts and 22 singles in the Irish charts.  The group have had 6 UK number one singles and 9 number one singles in Ireland with 12 of their 24 singles in the UK being in the UK Top 2.  Boyzone are one of the most successful bands in Ireland and the United Kingdom.  In total, Boyzone had 19 top 5 singles on the Irish Singles Chart, 18 top 10 hits on the UK Singles Chart, nine No. 1 Irish hit singles and six No. 1 UK hit singles and five No. 1 albums, with 25 million records sold by 2013 worldwide. "Like It Like That" is the title track and first single from Australian pop, R&B and soul singer-songwriter Guy Sebastian's fifth album "Like It Like That".  It was co-written by Sebastian, David Ryan Harris and Sean Hurley.  "Like It Like That" was released on 13 August 2009 and peaked at number one on the ARIA singles chart.  It was Sebastian's fourth of six number one singles and fifth of 12 top ten singles in Australia.  It was the highest selling Australian artist single and sixth highest selling single overall in Australia in 2009.  It received a 2010 ARIA Music Award nomination for Most Popular Australian Single.  In 2014 the song reached 4× platinum certification.  "Like It Like That" also charted in New Zealand in 2011, peaking at number 30 and gaining gold certification there. <ref name="Latest Gold/Platinum Singles">Latest Gold/Platinum Singles.  RadioScope New Zealand.  Archived from the original on 24 July 2011.  Retrieved 15 January 2012. </ref> The discography of Colombian Latin pop singer and songwriter Shakira consists of ten studio albums, three compilation albums, two live albums and two promotional albums. Shakira has also released 39 singles, two extended plays, 35 music videos and three music DVDs.  Shakira released two promotional albums "Magia" (1990) and "Peligro" (1993), before releasing her debut album "Pies Descalzos" in 1996.  It debuted at number one in eight different countries and went on to sell five million copies worldwide.  The album spawned six singles, "Estoy Aquí", "¿Dónde Estás Corazón? ", "Pies Descalzos, Sueños Blancos", "Un Poco de Amor", "Antología" and "Se Quiere, Se Mata".  The next year, a remix album, simply titled "The Remixes" was released, featuring remixes of songs from her debut album.  Shakira's second studio album "Dónde Están los Ladrones? " was released in September 1998.  The album debuted at number 131 on the "Billboard" 200 and went on to sell 7 million copies worldwide.  Eight of the eleven tracks on the album's became singles: "Ciega, Sordomuda", "Si Te Vas", "Tú", "Inevitable", "Octavo Día", "Moscas en la Casa", "No Creo" and "Ojos Así". Gary Barlow OBE (born 20 January 1971) is an English singer, songwriter and record producer.  He is frontman and lead vocalist of British pop-group Take That.  Barlow also served as head judge of "The X Factor UK" from 2011 to 2013 and "Let It Shine" in 2017.  Barlow is one of Britain's most successful songwriters, having written fourteen number one singles and twenty-four top 10 hits.  He has had three number one singles, six top 10 singles and two number one albums as a solo artist, and has had seventeen top 5 hits, twelve number one singles and seven number one albums with Take That.  He is also a six-time recipient of the Ivor Novello Award and has sold over 50 million records worldwide.
Answer: Hillary Lindsey