package no132;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Vector3 p = new Vector3(sc.nextDouble(), sc.nextDouble(), sc.nextDouble());
		Vector3[] x = new Vector3[n];
		for(int i=0;i<n;i++) {
			x[i] = new Vector3(sc.nextDouble(), sc.nextDouble(), sc.nextDouble());
		}
		double ans = 0;
		for(int i=0;i<n;i++) {
			for(int j=i+1;j<n;j++) {
				for(int k=j+1;k<n;k++) {
					Vector3 v1 = x[j].subtract(x[i]);
					Vector3 v2 = x[k].subtract(x[i]);
					Vector3 r = p.subtract(x[i]);
					Vector3 t = v1.cross(v2).normalize();
					ans += Math.abs(r.dot(t));
				}
			}
		}
		System.out.println(ans);
	}

}

class Vector3 {
	public static final Vector3 ZERO = new Vector3(0, 0, 0);
	public double x;
	public double y;
	public double z;
	public Vector3(double x,double y,double z) {
		this.x = x;
		this.y = y;
		this.z = z;
	}
	public double dot(Vector3 v) {
		return x * v.x + y * v.y + z * v.z;
	}
	public Vector3 cross(Vector3 v) {
		return new Vector3(y * v.z - z * v.y, z * v.x - x * v.z, x * v.y - y * v.x);
	}
	public Vector3 add(Vector3 v) {
		return new Vector3(x + v.x, y + v.y, z + v.z);
	}
	public Vector3 subtract(Vector3 v) {
		return new Vector3(x - v.x, y - v.y, z - v.z);
	}
	public Vector3 multiply(double k) {
		return new Vector3(k * x, k * y, k * z);
	}
	public double normSq() {
		return x * x + y * y + z * z;
	}
	public double norm() {
		return Math.sqrt(normSq());
	}
	public Vector3 normalize() {
		return multiply(1 / norm());
	}
	public boolean isZero() {
		return x == 0 && y == 0 && z == 0;
	}
	public boolean equals(Object o) {
		if (o instanceof Vector3) {
			Vector3 v = (Vector3) o;
			return x == v.x && y == v.y && z == v.z;
		}
		return super.equals(o);
	}
	public String toString() {
		return "[" + this.x + "," + this.y + "," + this.z + "]";
	}
}