Recently, Goni read a book by Plato. Inspired by Plato's life, he decided to invent a theorem related to geometry. While attempting to prove his own theorem, he encountered a problem and needs help to solve it.





Here the center of this circle is O(0,0).  OA lies on X axis. And CB || OA . You have to find the area of ABCO.
INPUT: The first line contains two integers  x,y, denoted the coordinate of C(x,y).
The next line contain one integer r .denoted the radius of this circle.
OUTPUT : Print  the area of ABCO . The value calculated must be presented with 3 digits after the decimal point.
Sample input:
  1 1 
 2

Sample output:
1.047


Sample input:
 3 8 
25
 
Sample output:


101.790