#include <iostream>
#include <iomanip>
#include <cmath>
#include <vector>

#define FORR(i,b,e) for(int i=(b);i<(int)(e);++i)
#define FOR(i,e) FORR(i,0,e)
#define dump(var) cerr << #var ": " << var << "\n"
#define dumpc(con) for(auto& e: con) cerr << e << " "; cerr<<"\n"

typedef long long ll;
typedef unsigned long long ull;

using namespace std;

struct Vector3D {
    double x, y, z;

    Vector3D(){}
    Vector3D(double x, double y, double z): x(x), y(y), z(z) {}
    Vector3D(const Vector3D &v) {
        x = v.x; y = v.y; z = v.z;
    }

    Vector3D operator+(const Vector3D &v) const {
        return Vector3D(x+v.x, y+v.y, z+v.z);
    }
    Vector3D operator-(const Vector3D &v) const {
        return Vector3D(x-v.x, y-v.y, z-v.z);
    }

    double length() { return sqrt(x*x+y*y+z*z); }
    void normalize() {
        double l = length();
        x/=l; y/=l; z/=l;
    }

    double dot(const Vector3D &v) {
        return x*v.x + y*v.y + z*v.z;
    }

    Vector3D cross(const Vector3D &v) {
        return Vector3D(y * v.z - z * v.y,
                        z * v.x - x * v.z,
                        x * v.y - y * v.x);
    }
};


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N;
    cin >> N;
    Vector3D p;
    vector<Vector3D> v(N);
    cin >> p.x >> p.y >> p.z;
    FOR(i, N) cin >> v[i].x >> v[i].y >> v[i].z;

    Vector3D vp, v1, v2, normal;
    double length = 0;
    v1 = v[1] - v[0];
    FOR(i, N) FOR(j, i) {
        vp = v[i] - p;
        v1 = v[j] - v[i];
        FOR(k, j) {
            v2 = v[k] - v[j];
            normal = v1.cross(v2);
            normal.normalize();
            length += abs(vp.dot(normal));
        }
    }

    cout << fixed << setprecision(10);
    cout << length << endl;
    
    return 0;
}