#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v, w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int N; cin >> N;
	double px, py, pz;
	cin >> px >> py >> pz;
	vector<double> x(N), y(N), z(N);
	for (int i = 0; i < N; i++)
		cin >> x[i] >> y[i] >> z[i];
	double sum = 0;
	for (int i = 0; i < N; i++)
		for (int j = i + 1; j < N; j++)
			for (int k = j + 1; k < N; k++) {
				double a11 = x[i] - px, a12 = x[j] - px, a13 = x[k] - px;
				double a21 = y[i] - py, a22 = y[j] - py, a23 = y[k] - py;
				double a31 = z[i] - pz, a32 = z[j] - pz, a33 = z[k] - pz;
				double det = a11*a22*a33 + a12*a23*a31 + a13*a21*a32 - a11*a23*a32 - a12*a21*a33 - a13*a22*a31;
				
				double dx1 = x[i] - x[j], dx2 = x[j] - x[k], dx3 = x[k] - x[i];
				double dy1 = y[i] - y[j], dy2 = y[j] - y[k], dy3 = y[k] - y[i];
				double dz1 = z[i] - z[j], dz2 = z[j] - z[k], dz3 = z[k] - z[i];
				double a = sqrt(dx1 * dx1 + dy1 * dy1 + dz1 * dz1);
				double b = sqrt(dx2 * dx2 + dy2 * dy2 + dz2 * dz2);
				double c = sqrt(dx3 * dx3 + dy3 * dy3 + dz3 * dz3);
				double s = (a + b + c) / 2;
				double S = sqrt(s * (s - a) * (s - b) * (s - c));

				sum += abs(det) / S;
			}
	printf("%.10f\n", sum / 2);
}