import std.algorithm, std.array, std.container, std.range, std.bitmanip;
import std.numeric, std.math, std.bigint, std.random, core.bitop;
import std.string, std.regex, std.conv, std.stdio, std.typecons;

struct point {
  real x, y, z;
}

void main()
{
  auto n = readln.chomp.to!size_t;
  auto ai = iota(n + 1)
    .map!(_ => readln.split.map!(to!real))
    .map!(rd => point(rd[0], rd[1], rd[2])).array;
  auto p = ai.front;
  auto qi = ai[1..$];

  auto bi = new bool[](n);
  bi[3..$] = true;

  real s = 0;
  do {
    auto r = qi.zip(bi).filter!("!a[1]").map!("a[0]").array;

    auto a = (r[1].y - r[0].y) * (r[2].z - r[0].z) - (r[2].y - r[0].y) * (r[1].z - r[0].z);
    auto b = (r[1].z - r[0].z) * (r[2].x - r[0].x) - (r[2].z - r[0].z) * (r[1].x - r[0].x);
    auto c = (r[1].x - r[0].x) * (r[2].y - r[0].y) - (r[2].x - r[0].x) * (r[1].y - r[0].y);
    auto d = -(a * r[0].x + b * r[0].y + c * r[0].z);

    auto t = (a * p.x + b * p.y + c * p.z + d).abs / (a ^^ 2 + b ^^ 2 + c ^^ 2).sqrt;
    s += t;
  } while(bi.nextPermutation);

  writefln("%.9f", s);
}