Quick geometry question for you: How many sides does a triangle have? Yes, the answer is three — thank you, "Sesame Street" — so if you're going to make a film about a love triangle, you're going to need three people. It's simple math.

Well, Oscar winning writer/director Paul Haggis just landed one side to his triangle, as The Wrap is reporting that Mila Kunis has signed on to star in "Third Person."

Sexiest. Hypotenuse. Ever.

Of course, there's still the matter of just whose angles she'll be dangling; Liam Neeson, Olivia Wilde and Naomi Watts have already reportedly joined the cast, but with Casey Affleck and James Franco both reportedly in talks to join the project as well, somebody's going to be on the outside looking in. Assuming, of course, that Haggis doesn't decide to make the world's first ever love hexagon, which would almost certainly demand an NC-17 rating.

Whatever the case, we'll find out soon enough, as "Third Person" is set to begin filming in October, with three interconnected love stories — and thus the potential for all sorts of geometric shenanigans — taking place in three of the world's sexiest cities, New York, Paris and Rome.

Looks like it's no longer hip to be square.

Slideshow: Sexy Mila Kunis Photos