// Enjoy your stay.

#include <bits/stdc++.h>

#define EPS 1e-9
#define INF 1070000000LL
#define MOD 1000000007LL
#define fir first
#define foreach(it,X) for(auto it=(X).begin();it!=(X).end();it++)
#define ite iterator
#define mp make_pair
#define mt make_tuple
#define rep(i,n) rep2(i,0,n)
#define rep2(i,m,n) for(int i=m;i<(n);i++)
#define pb push_back
#define sec second
#define sz(x) ((int)(x).size())

using namespace std;

typedef istringstream iss;
typedef long long ll;
typedef pair<ll,ll> pi;
typedef stringstream sst;
typedef vector<ll> vi;

// geometry library from hos

const double PI = acos(-1);

int sig(double r) { return (r < -EPS) ? -1 : (r > +EPS) ? +1 : 0; }

struct PT {
	double x, y, z;
	PT() {}
	PT(double x, double y, double z) : x(x), y(y), z(z) {}
	PT operator+(const PT &a) const { return PT(x + a.x, y + a.y, z + a.z); }
	PT operator-(const PT &a) const { return PT(x - a.x, y - a.y, z - a.z); }
	PT operator-() const { return PT(-x, -y, -z); }
	PT operator*(const double &k) const { return PT(x * k, y * k, z * k); }
	PT operator/(const double &k) const { return PT(x / k, y / k, z / k); }
	double abs() const { return sqrt(x * x + y * y + z * z); }
	double abs2() const { return x * x + y * y + z * z; }
	double dot(const PT &a) const { return x * a.x + y * a.y + z * a.z; }
	PT cross(const PT a) const { return PT(y * a.z - z * a.y, z * a.x - x * a.z, x * a.y - y * a.x); }
	bool operator<(const PT &a) const { return (x != a.x) ? (x < a.x) : (y != a.y) ? (y < a.y) : (z < a.z); }
	bool operator==(const PT &a) const { return (sig(x - a.x) == 0) && (sig(y - a.y) == 0) && (sig(z - a.z) == 0); }
};
ostream &operator<<(ostream &os, const PT &a) { os << "(" << a.x << ", " << a.y << ", " << a.z << ")"; return os; }
PT tri(PT a, PT b, PT c) { return (b - a).cross(c - a); }
double tet(PT a, PT b, PT c, PT d) { return (b - a).cross(c - a).dot(d - a); }

double dLP(PT a, PT b, PT c) {
	return tri(a, b, c).abs() / (b - a).abs();
}
double dSP(PT a, PT b, PT c) {
	if (sig((b - a).dot(c - a)) <= 0) return (c - a).abs();
	if (sig((a - b).dot(c - b)) <= 0) return (c - b).abs();
	return tri(a, b, c).abs() / (b - a).abs();
}

// end of library

double triangle(double a,double b,double c){
	double s = (a+b+c)/2;
	return sqrt(s*(s-a)*(s-b)*(s-c));
}

int main(){
	int N;
	PT p,q[333];
	cin>>N;
	cin>>p.x>>p.y>>p.z;
	rep(i,N){
		cin>>q[i].x>>q[i].y>>q[i].z;
	}
	double ans = 0;
	rep(i,N)rep2(j,i+1,N)rep2(k,j+1,N){
		double V = tet(p,q[i],q[j],q[k]);
		double t = triangle((q[i]-q[j]).abs(),(q[j]-q[k]).abs(),(q[k]-q[i]).abs());
		ans += abs(V/t);
	}
	cout<<setprecision(16)<<ans/2<<endl;
}