# The Cheese for Anfisa

The master was making dinner for Anfisa which symbolize 2008 year. He used a special knife which cuts up the cheese on the identical rectangular parallelepipeds with basis like square with the side of $A$ and the high $B$.

But Anfisa liked to use cheese with size less then master did as well as becomes to the lady of year. Anfisa always establishes the cheese strictly vertical and by a square to the table and cuts the offered piece of sweets on two parts. When Anfisa cuts the pieces of cheese the knife always took a place on a diagonal of the square. But Anfisa not always can cut a piece in a half because the plane of blade of the knife formed the dihedral angle of $Z°$ with the plane of basis.

You have find the area $S$ of the figure which formed by Anfisa when she cuts the piece.

## Input

Three integers $A$, $B$, $Z$, no more than $90$.

## Output

The area $S$ of the figure formed by Anfisa when she cuts the piece; print the area with 3 digits after the decimal point.