Question: Which American singer-songwriter that had 15 number one singles in 2015 helped Shakira write Medicine?

"Medicine" is a song recorded by Colombian singer and songwriter Shakira from her tenth studio album "Shakira" (2014).  The song was written by Shakira alongside Mark Bright and Hillary Lindsey, while the production was handled by Shakira and busbee.  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. <SEP>  As of 2015, she has had 15 number one singles as a writer. 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. <SEP> "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> <SEP> 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".