Question: The co-writer of the song "Firework" also wrote which song by singer Chris Brown?
Context: "Loyal" is a song by American singer Chris Brown, released as the fourth single from his sixth studio album "X" (2014).  The song was produced by Nic Nac and features a guest appearance from fellow rapper Lil Wayne and another rapper depending on the version.  French Montana and Too Short feature on the East and West Coast version while Tyga features on the video and album version.  "Loyal" peaked at number nine on the US "Billboard" Hot 100.  It stayed on the chart for 36 weeks.The song was promoted with performances by Brown and Lil Wayne at the BET Awards 2014, Summer Jam, 2014 Soul Train Music Awards, and "The Tonight Show Starring Jimmy Fallon".  This also marks the fifth Chris Brown and Lil Wayne collaboration and the second Chris Brown and Tyga collaboration. "Firework" is a song by American singer Katy Perry from her third studio album, "Teenage Dream" (2010).  Perry co-wrote the song with Ester Dean and its producers StarGate and Sandy Vee.  It is a dance-pop self-empowerment anthem with inspirational lyrics, and Perry felt it was an important song for her on "Teenage Dream".  Capitol Records released it as the album's third single on October 26, 2010. "Yo (Excuse Me Miss)" is a song recorded by American singer Chris Brown.  It served as the second single from Brown's debut album "Chris Brown" (2005) and was released in November 2005 in the US and February 2006 worldwide.  "Yo (Excuse Me Miss)", produced by Dre & Vidal, became Brown's second top ten single in the United States, peaking at number seven on the US Billboard Hot 100. Esther Renay Dean (born April 15, 1982), known professionally as Ester Dean, is an American singer, songwriter, record producer, and actress.  Her 2009 single "Drop It Low" featured singer Chris Brown.  Dean has also co-written songs for many artists including Christina Aguilera, Florence + The Machine, Katy Perry, Beyoncé, Nicole Scherzinger, Priyanka Chopra, Mary J. Blige, Nicki Minaj, Kelly Clarkson, Ciara, The Pussycat Dolls, Usher, Kelly Rowland, Girlicious, Keri Hilson, Rihanna, R. Kelly, Britney Spears, Melody Thornton, Vanessa White, Kevin McHale, Selena Gomez, G.R.L., Soulja Boy Tell 'Em, Little Mix, Pia Toscano, Tinie Tempah, Lil Wayne, Machine Gun Kelly, Fifth Harmony, and Eurovision Song Contest 2012 winner Loreen. "Beautiful People" is a song by American singer Chris Brown featuring Italian DJ Benny Benassi, released as the third single from Brown's fourth studio album "F.A.M.E." on March 11, 2011.  It was written by Brown, Jean Baptiste, Marco Benassi and Allessandro Benassi, and was produced by the latter two.  Musically, "Beautiful People" is an uptempo song which draws from the genres of electro house, dancehall and Europop, and contains influences of R&B.  The song's lyrics revolve around Brown encouraging "everyone on the dance floor to keep their heads up and discover the beauty inside." "As Your Friend" is a song by Dutch DJ Afrojack, featuring vocals by American singer Chris Brown.  The song was released as a single via iTunes on 13 February 2013.  It was written by Afrojack, Chris Brown, Nadir Sakir, Leroy Styles, DJ Buddha, and Polow Da Don, and was produced by Afrojack with co-production by Leroy Styles, DJ Buddha and Polow da Don.  "As Your Friend" is featured as a bonus track on the deluxe version of Afrojack's 2014 debut studio album "Forget the World". "Drop It Low" is a buzz single by American singer songwriter Ester Dean.  The official version features vocals from R&B singer Chris Brown.  This is also released as the second single from the soundtrack for the film "More Than a Game" (2009).  The original version of the song did not have Chris Brown featured.  This version maintains the same lyrics on the second verse but coming from a man's perspective.  The official remix features Lil Wayne, Trey Songz and Diddy.  Polow da Don later stated that the song was originally meant for Ciara, but when the singer passed on it, it was eventually given to Ester Dean. Why Stop Now is a song by American rapper Busta Rhymes, released November 16, 2011, as a Promotional single.  The song, produced by Sak Pase, features fellow American singer Chris Brown.  Busta Rhymes uses his signature fast-paced rapping in all three verses, over production that contains elements of techno music.  Chris Brown sings the chorus with aggression.  The song was released after his last single "Stop the Party" which featured American rapper and record producer Swizz Beatz.  The song was released as a free launch exclusive for Google Music, and is only available digitally through that marketplace. "Freeze" is the third and final single from R&B singer T-Pain from his third album, "Thr33 Ringz".  The song features singer Chris Brown.  The song was released on iTunes on October 10 and was added to T-Pain's MySpace on October 17.  A version that features Omarion was originally on the album, but was changed to Chris Brown. "Ayo" is a song by American singer Chris Brown and American rapper Tyga (billed together as "Chris Brown X Tyga"), released as the lead single from their collaboration album "".  It was produced by Nic Nac and Mark Kragen, whom the former Chris previously worked with on "Loyal".
Answer: "Drop It Low"