Problem Statement

The animation club of a certain high school was making a pledge over donuts in preparation for the school festival.
Since they are high school girls, they are concerned about calories. However, the donuts they bought had no calorie information listed.
Viewed from above, the donuts they bought look like a perfect pair of concentric circles, and cutting through the ring of the donut gives a perfect circle. (In other words, the donut is a torus.)
So they decided to find the calories using the fact that the donut has \(C\)kcal per \(1cm^{3}\).

Input

\(C\)
\(R_{in}\ R_{out}\)

\(C\) is the calories per \(1cm^3\) of the donut. (C is an integer, \(0 \leq C \leq 10\) )
\(R_{in}\) is the radius (cm) of the inner circle when the donut is viewed from directly above. (\(R_{in}\) is a positive integer, \(1 \leq R_{in} \leq 20\))
\(R_{out}\) is the radius (cm) of the outer circle when the donut is viewed from directly above. (\(R_{out}\) is a positive integer, \(R_{in} \leq R_{out} \leq 20\))

Output

Output the calories of the donut they bought.
An error of up to \(10^{-5}\) is allowed. Do not forget the newline at the end.

Sample

0
5 10

0.0000000000

10
1 20

187053.6774116461

Hint