open System
open Microsoft.FSharp.Core

[<Measure>] type cal
[<Measure>] type cm
let R() = stdin.ReadLine()
let toMeasure = LanguagePrimitives.FloatWithMeasure

let C = R() |> float |> fun x -> toMeasure x:float<cal/cm^3>
let Rin, Rout = 
    let t = R().Split() |> Array.map float |> Array.map (fun x -> toMeasure x:float<cal/cm^3>)
    t.[0], t.[1]

let V = 0.25 * Math.PI ** 2.0 * (Rout + Rin) * (Rout - Rin) * (Rout - Rin)

V * C |> stdout.WriteLine