Hot 100 March Madness Finals: Vote Now!
Hot 100 March Madness Finals: Vote Now!

Britney and Gaga moved on, LMFAO fell hard (twice), and Katy Perry won some and lost some: Round 1 of Billboard.com's Hot 100 March Madness is over, with 16 No. 1 Hot 100 singles moving on to the second round from the field of 32. With the first round of head-to-head match-ups completed, it's time for some more voting!

To help determine the winner of Hot 100 March Madness, check out the updated bracket of songs, and vote for your favorites in the head-to-head match-ups below.

The original bracket was comprised of the 32 most recent songs to top the Hot 100 chart. The match-ups within the bracket were determined by the dates in which each song topped the Hot 100: the most recent No. 1, fun.'s "We Are Young," is matched up against the 32nd most recent No. 1, Rihanna's "Rude Boy," and so on. Click here to see the original bracket.

On Tuesday (Mar. 20), we'll reveal the 8 songs that won their second-round match-ups, and another round of voting begins. On Friday, Mar. 30, a Hot 100 March Madness champion -- the No. 1 single that you think is the best smash hit of the past two years -- will be crowned.

Looking back at the exciting first round of voting, the pop divas reigned supreme, with Lady Gaga, Britney Spears, Ke$ha, Katy Perry, Rihanna, Adele and Pink making up over half of the Sweet 16. LMFAO, who had two songs competing with "Party Rock Anthem" and "Sexy and I Know It," couldn't get either to stick, and got stomped by Ke$ha's "We R Who We R" and Katy Perry's "California Gurls," respectively.

Meanwhile, Rihanna's longest Hot 100 No. 1, "We Found Love," also couldn't make it out of the first round -- but we won't stand here and watch her cry, since the song that trumped "Love," Eminem's "Love The Way You Lie," features the pop star on the hook. Speaking of Eminem, the rapper was the victim of the closest race of the competition thus far, as Adele's "Set Fire To The Rain" barely squeaked by "Not Afraid." And Katy Perry's six No. 1 singles yielded three spots in the Sweet 16, with "Last Friday Night (T.G.I.F.)," "Part of Me" and "E.T." falling out but "California Gurls," "Teenage Dream" and "Firework" shining bright.

Vote now for your favorite tracks below, and be sure to discuss the bracket in the comments section!