3 (Britney Spears song)
"3" is a song recorded by American singer Britney Spears.  It is from her second greatest-hits album, The Singles Collection.  "3" was released to American radio on September 29, 2009. It is about a threesome, with a hook that references the music group Peter, Paul and Mary.  It was written by Max Martin, Shellback, and Tiffany Amber, while Martin and Shellback produced it.