import scala.io.StdIn

class Vector3(_x: Double, _y: Double, _z: Double) {
  val (x, y, z) = (_x, _y, _z)
  def this() = this(0, 0, 0)
  def this(a: Array[Double]) = this(a(0), a(1), a(2))
  def -(o: Vector3): Vector3 = new Vector3(x - o.x, y - o.y, z - o.z)
  def cross_product(o: Vector3): Vector3 = new Vector3(y * o.z - z * o.y, z * o.x - x * o.z, x * o.y - y * o.x)
  def inner_product(o: Vector3): Double = x * o.x + y * o.y + z * o.z
  def norm(): Double = scala.math.sqrt(x * x + y * y + z * z)
}

object Main extends App {
  val n: Int = StdIn.readInt()
  val p: Vector3 = new Vector3(StdIn.readLine().split(" ").map(_.toDouble))
  val l = (1 to n).map(_ => new Vector3(StdIn.readLine().split(" ").map(_.toDouble)) - p)
  val ans = l.combinations(3).map { a =>
    val t = (a(1) - a(0)).cross_product(a(2) - a(0))
    scala.math.abs(a(0).inner_product(t)) / t.norm
  }.sum
  println(ans)
}