#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <cassert>
#include <limits>
#include <functional>
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) __typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define all(o) (o).begin(), (o).end()
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset(m,v,sizeof(m))
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
using namespace std;
typedef vector<int> vi; typedef pair<int,int> pii; typedef vector<pair<int,int> > vpii; typedef long long ll;
template<typename T, typename U> inline void amin(T &x, U y) { if(y < x) x = y; }
template<typename T, typename U> inline void amax(T &x, U y) { if(x < y) x = y; }

struct Point {
	double x, y, z;
};

double sq(double x) { return x * x; }

int main() {
	int N;
	while(~scanf("%d", &N)) {
		Point org;
		scanf("%lf%lf%lf", &org.x, &org.y, &org.z);
		vector<Point> points(N);
		rep(i, N) {
			Point p;
			scanf("%lf%lf%lf", &p.x, &p.y, &p.z);
			p.x -= org.x;
			p.y -= org.y;
			p.z -= org.z;
			points[i] = p;
		}
		vector<vector<double> > dist(N, vector<double>(N));
		rep(i, N) rep(j, i) {
			const Point &p = points[i], &q = points[j];
			dist[i][j] = sqrt(sq(p.x - q.x) + sq(p.y - q.y) + sq(p.z - q.z));
		}
		double ans = 0;
		rep(i, N) reu(j, i + 1, N) reu(k, j + 1, N) {
			const double A[3][3] = {
				{ points[i].x, points[i].y, points[i].z },
				{ points[j].x, points[j].y, points[j].z },
				{ points[k].x, points[k].y, points[k].z },
			};
			double a = dist[j][i], b = dist[k][j], c = dist[k][i];
			double s = (a + b + c) / 2;
			double area = sqrt(s * (s - a) * (s - b) * (s - c));
			double det = 0;
			det += A[0][0] * A[1][1] * A[2][2];
			det -= A[0][0] * A[1][2] * A[2][1];
			det -= A[0][1] * A[1][0] * A[2][2];
			det += A[0][1] * A[1][2] * A[2][0];
			det += A[0][2] * A[1][0] * A[2][1];
			det -= A[0][2] * A[1][1] * A[2][0];
			double height = abs(det) / 2 / area;
			ans += height;
		}
		printf("%.10f\n", ans);
	}
	return 0;
}