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Surprise! Rihanna dropped a brand new song via her social networks Saturday night, and it's a big one. "FourFiveSeconds" features Kanye West and Paul McCartney, and we are already LOVING IT!

[Buy "FourFiveSeconds" on iTunes]

The acoustic ballad features vocals from Rihanna and Kanye, and we're guessing that's Paul MCartney on guitar or keys. The song is sans drums - and has a "we're all besties sitting around the campfire" vibe. If this is any indication of what's in store from Rihanna's upcoming album, WE. CAN'T. WAIT.

On Saturday night, Rihanna tweeted this photo with Paul McCartney and Kanye West

She soon followed it up with another tweet:

Check out the song and let us know what you think in the comments below! Are you digging the collaboration between RiRi, Kanye and Sir Paul?