#include <iostream>
#include <algorithm>
#include <iomanip>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>

static const int MOD = 1000000007;
using ll = long long;
using u32 = uint32_t;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max()/32*15+208;

using real = double;
static constexpr real EPS = 1e-10;
struct Point3 {
    real x, y, z;
    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 real k) { x *= k; y *= k; z *= k;  return *this; }
    Point3& operator/=(const real k) { x /= k; y /= k; z /= k; return *this; }
    Point3 operator+(const Point3 a) const {return Point3(*this) += a; }
    Point3 operator-(const Point3 a) const {return Point3(*this) -= a; }
    Point3 operator*(const real k) const {return Point3(*this) *= k; }
    Point3 operator/(const real k) const {return Point3(*this) /= k; }
    Point3 (real a = 0, real b = 0, real c = 0) : x(a), y(b), z(c) {};
};

inline real dot(Point3 a, Point3 b){ return a.x*b.x + a.y*b.y + a.z*b.z; }
inline real abs(Point3 a){ return sqrt(dot(a, a)); }
inline Point3 cross(Point3 a, Point3 b){ return {a.y*b.z-a.z*b.y, a.z*b.x-a.x*b.z, a.x*b.y-a.y*b.x};  }

istream& operator>> (istream& s, Point3& P){
    s >> P.x >> P.y >> P.z;
    return s;
}

int main() {
    int n;
    cin >> n;
    Point3 P;
    cin >> P;
    vector<Point3> v(n);
    for (auto &&i : v) {
        cin >> i;
        i -= P;
    }
    real 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) {
                ans += abs(dot(v[i], cross(v[j], v[k]))/abs(cross(v[j]-v[i], v[k]-v[i])));
            }
        }
    }
    printf("%.15lf\n", ans);
    return 0;
}