import kotlin.math.PI


fun main(arr:Array<String>) {
    val cal = readLine()!!.toInt()
    val (inR, outR) = readLine()!!.split(" ").map { it.toInt() }
    var ans = PI * PI / 4 * (inR+outR)*(outR-inR)*(outR-inR)
    println(ans*cal)
}