//#include <tourist>
#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef pair<ll, ll> p;
const int INF = 1e9;
const ll LINF = ll(1e18);
const int MOD = 1000000007;
const int dx[4] = {0, 1, 0, -1}, dy[4] = {-1, 0, 1, 0};
const int Dx[8] = {0, 1, 1, 1, 0, -1, -1, -1}, Dy[8] = {-1, -1, 0, 1, 1, 1, 0, -1};
#define yes cout << "Yes" << endl
#define YES cout << "YES" << endl
#define no cout << "No" << endl
#define NO cout << "NO" << endl
#define rep(i, n) for (int i = 0; i < n; i++)
#define ALL(v) v.begin(), v.end()
#define debug(v)          \
    cout << #v << ":";    \
    for (auto x : v)      \
    {                     \
        cout << x << ' '; \
    }                     \
    cout << endl;
template <class T>
bool chmax(T &a, const T &b)
{
    if (a < b)
    {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b)
{
    if (b < a)
    {
        a = b;
        return 1;
    }
    return 0;
}
//cout<<fixed<<setprecision(15);有効数字15桁
//-std=c++14
//g++ yarudake.cpp -std=c++17 -I .
ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    int n;
    cin >> n;
    double px, py, pz;
    vector<double> x(n), y(n), z(n);
    cin >> px >> py >> pz;
    double ps = sqrt(px * px + py * py + pz * pz);
    rep(i, n) cin >> x[i] >> y[i] >> z[i];
    double ans = 0;
    rep(i, n)
    {
        for (int j = i + 1; j < n; j++)
        {
            for (int k = j + 1; k < n; k++)
            {
                double vx, vy, vz;
                double ux, uy, uz;
                vx = x[j] - x[i];
                vy = y[j] - y[i];
                vz = z[j] - z[i];
                ux = x[k] - x[i];
                uy = y[k] - y[i];
                uz = z[k] - z[i];
                double rx, ry, rz; //法線ベクトル
                rx = vy * uz - vz * uy;
                ry = vz * ux - vx * uz;
                rz = vx * uy - vy * ux;
                double temp = abs(rx * (px - x[i]) + ry * (py - y[i]) + rz * (pz - z[i]));
                temp /= sqrt(rx*rx+ry*ry+rz*rz);
                ans+=temp;
            }
        }
    }
    cout << fixed << setprecision(15);
    cout << ans << "\n";
}