#include<bits/stdc++.h>
using namespace std;

typedef long long int ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pair<int, int> > vii;
#define rrep(i, m, n) for(int (i)=(m); (i)<(n);  (i)++)
#define erep(i, m, n) for(int (i)=(m); (i)<=(n); (i)++)
#define  rep(i, n)    for(int (i)=0; (i)<(n);  (i)++)
#define  rev(i, n)    for(int (i)=(n)-1; (i)>=0; (i)--)
#define vrep(i, c)    for(__typeof((c).begin())i=(c).begin(); i!=(c).end(); i++)
#define  ALL(v)       (v).begin(), (v).end()
#define mp            make_pair
#define pb            push_back
template<class T1, class T2> inline void minup(T1& m, T2 x){ if(m>x) m=static_cast<T2>(x); }
template<class T1, class T2> inline void maxup(T1& m, T2 x){ if(m<x) m=static_cast<T2>(x); }

#define INF 1000000000
#define MOD 1000000007
#define EPS 1E-12

const int MAX_N = 300;
double P[3];
double Q[MAX_N][3];
int n;
double res;

// 幾何ライブラリを作りたい.....
int main()
{
  cin >> n;

  cin >> P[0] >> P[1] >> P[2];
  rep(i, n) rep(j, 3) cin >> Q[i][j];
  rep(i, n) rep(j, 3) Q[i][j] -= P[j];

  rep(i, n) rep(j, i) rep(k, j){
    double Px = Q[j][0] - Q[i][0];
    double Py = Q[j][1] - Q[i][1];
    double Pz = Q[j][2] - Q[i][2];
    double Qx = Q[k][0] - Q[i][0];
    double Qy = Q[k][1] - Q[i][1];
    double Qz = Q[k][2] - Q[i][2];
    double dx = Py * Qz - Pz * Qy;
    double dy = Pz * Qx - Px * Qz;
    double dz = Px * Qy - Py * Qx;

    res += abs(Q[i][0]*dx + Q[i][1]*dy + Q[i][2]*dz) / sqrt(dx*dx + dy*dy + dz*dz);
  }

  printf("%.10f\n", res);

  return 0;
}