#include <iostream>
#include <iomanip>
#include <fstream>
#include <vector>
#include <cmath>
using namespace std;

template<typename T>
class Point3
{
public:
	T x, y, z;

	Point3() {}
	
	Point3(T x, T y, T z) : x(x), y(y), z(z) {}
	
	Point3(const Point3& src) : x(src.x), y(src.y), z(src.z) {}
	
	Point3 operator-() const {
		return Point3(-x, -y, -z);
	}

	Point3& operator=(const Point3& a) {
		if (&a != this) {
			x = a.x;
			y = a.y;
			z = a.z;
		}
		return *this;
	}
	
	Point3& operator+=(const Point3& a)	{
		x += a.x;
		y += a.y;
		z += a.z;
		return *this;
	}

	Point3& operator-=(const Point3& a)	{
		x -= a.x;
		y -= a.y;
		z -= a.z;
		return *this;
	}

	Point3 operator+(const Point3& a) const {
		Point3 r = *this;
		r += a;
		return r;
	}

	Point3 operator-(const Point3& a) const {
		Point3 r = *this;
		r -= a;
		return r;
	}
};

typedef Point3<double> Point3d;

istream& operator>>(istream& in, Point3d& p)
{
	in >> p.x >> p.y >> p.z;
	return in;
}

template<typename T, size_t N>
class Vec
{
public:
	T val[N];
	
	T& operator[](size_t k) {
		return val[k];
	}

	const T& operator[](size_t k) const {
		return val[k];
	}

	Vec() {}
	Vec(T a1) { val[0] = a1; }
	Vec(T a1, T a2) { val[0] = a1; val[1] = a2; }
	Vec(T a1, T a2, T a3) { val[0] = a1; val[1] = a2; val[2] = a3; }
	Vec(T a1, T a2, T a3, T a4) { val[0] = a1; val[1] = a2; val[2] = a3; val[3] = a4; }

	Vec(const Vec& src) {
		for (size_t i = 0; i < N; i++) {
			val[i] = src.val[i];
		}
	}

	Vec& operator=(const Vec& src) {
		if (&src != this) {
			for (size_t i = 0; i < N; i++) {
				val[i] = src.val[i];
			}
		}
	}

	Vec& operator+=(const Vec& a) {
		for (size_t i = 0; i < N; i++) {
			val[i] += a.val[i];
		}
	}

	Vec& operator-=(const Vec& a) {
		for (size_t i = 0; i < N; i++) {
			val[i] -= a.val[i];
		}
	}
};

template<typename T>
class Vec3 : public Vec < T, 3 >
{
public:
	Vec3(const Point3<T>& src) : Vec<T,3>(src.x, src.y, src.z) {}
};

typedef Vec3<double> Vec3d;

template<typename T, size_t N>
T dot(const Vec<T, N>& a, const Vec<T, N>& b)
{
	T sum = 0;
	for (int i = 0; i < N; i++) {
		sum += a[i] * b[i];
	}
	return sum;
}

class Plane
{
public:
	double a, b, c, d;
	
	Plane() {}
	Plane(double a, double b, double c, double d) : a(a), b(b), c(c), d(d) {}
	Plane(const Point3d& p1, const Point3d& p2, const Point3d& p3)
	{
		Vec3d ab = p2 - p1;
		Vec3d ac = p3 - p1;
		a = ab[1] * ac[2] - ab[2] * ac[1];
		b = ab[2] * ac[0] - ab[0] * ac[2];
		c = ab[0] * ac[1] - ab[1] * ac[0];
		d = -(a * p1.x + b * p1.y + c * p1.z);
		double n = sqrt(a * a + b * b + c * c);
		a /= n;
		b /= n;
		c /= n;
		d /= n;
	}
};

int main()
{
#if 0
	ifstream in("test_in/len003.txt");
#define out cout
#else
#define in cin
#define out cout
#endif

	int n;
	in >> n;

	Point3d P;
	in >> P;

	vector<Point3d> Q(n);
	for (int i = 0; i < n; i++) {
		in >> Q[i];
		Q[i] -= P;
	}

	double sum = 0;
	for (int i = 0; i < n - 2; i++) {
		for (int j = i + 1; j < n - 1; j++) {
			for (int k = j + 1; k < n; k++) {
				Plane plane(Q[i], Q[j], Q[k]);
				double distance = fabs(plane.d);
				sum += distance;
			}
		}
	}
	out << fixed << setprecision(9) << sum << endl;
}