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#include <algorithm>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <limits>
#include <utility>
#include <vector>
using namespace std;

namespace {

template <typename Scalar, typename Scalar2=Scalar>
struct BasePoint {
  Scalar x;
  Scalar y;

  constexpr BasePoint(): x{0}, y{0}
  {
  }

  constexpr BasePoint(Scalar x_, Scalar y_): x{x_}, y{y_}
  {
  }

  template <typename OtherScalar, typename OtherScalar2>
  constexpr BasePoint(BasePoint<OtherScalar, OtherScalar2> const& p): x(p.x), y(p.y)
  {
  }
};

template <typename Scalar, typename Scalar2>
constexpr bool operator==(BasePoint<Scalar, Scalar2> const& p1, BasePoint<Scalar, Scalar2> const& p2)
{
  return p1.x == p2.x && p1.y == p2.y;
}

template <typename Scalar, typename Scalar2>
constexpr bool operator!=(BasePoint<Scalar, Scalar2> const& p1, BasePoint<Scalar, Scalar2> const& p2)
{
  return p1.x != p2.x || p1.y != p2.y;
}

template <typename Scalar, typename Scalar2=Scalar>
struct BaseVector {
  Scalar x;
  Scalar y;

  constexpr BaseVector(): x{0}, y{0}
  {
  }

  constexpr BaseVector(Scalar x_, Scalar y_): x{x_}, y{y_}
  {
  }

  template <typename OtherScalar, typename OtherScalar2>
  constexpr BaseVector(BaseVector<OtherScalar, OtherScalar2> const& v): x(v.x), y(v.y)
  {
  }

  int quadrant() const
  {
    if (x >= 0) {
      if (y >= 0) return 1;
      else return 4;
    } else {
      if (y >= 0) return 2;
      else return 3;
    }
  }
};

template <typename Scalar, typename Scalar2>
constexpr BaseVector<Scalar, Scalar2> operator+(BaseVector<Scalar, Scalar2> const& a, BaseVector<Scalar, Scalar2> const& b)
{
  return {a.x + b.x, a.y + b.y};
}

template <typename Scalar, typename Scalar2>
constexpr BaseVector<Scalar, Scalar2> operator-(BaseVector<Scalar, Scalar2> const& a, BaseVector<Scalar, Scalar2> const& b)
{
  return {a.x - b.x, a.y - b.y};
}

template <typename Scalar, typename Scalar2>
constexpr BaseVector<Scalar, Scalar2> operator+(BaseVector<Scalar, Scalar2> const& v)
{
  return v;
}

template <typename Scalar, typename Scalar2>
constexpr BaseVector<Scalar, Scalar2> operator-(BaseVector<Scalar, Scalar2> const& v)
{
  return {-v.x, -v.y};
}

template <typename Scalar, typename Scalar2>
constexpr BaseVector<Scalar, Scalar2> operator*(BaseVector<Scalar, Scalar2> const& v, Scalar s)
{
  return {s * v.x, s * v.y};
}

template <typename Scalar, typename Scalar2>
constexpr BaseVector<Scalar, Scalar2> operator*(Scalar s, BaseVector<Scalar, Scalar2> const& v)
{
  return {s * v.x, s * v.y};
}

template <typename Scalar, typename Scalar2>
constexpr Scalar2 operator*(BaseVector<Scalar, Scalar2> const& a, BaseVector<Scalar, Scalar2> const& b)
{
  return Scalar2{a.x} * b.x + Scalar2{a.y} * b.y;
}

template <typename Scalar, typename Scalar2>
constexpr Scalar operator%(BaseVector<Scalar, Scalar2> const& a, BaseVector<Scalar, Scalar2> const& b)
{
  return Scalar2{a.x} * b.y - Scalar2{a.y} * b.x;
}

template <typename Scalar, typename Scalar2>
constexpr BaseVector<Scalar, Scalar2> operator-(BasePoint<Scalar, Scalar2> const& a, BasePoint<Scalar, Scalar2> const& b)
{
  return {a.x - b.x, a.y - b.y};
}

template <typename Scalar, typename Scalar2>
constexpr BasePoint<Scalar, Scalar2> operator+(BaseVector<Scalar, Scalar2> const& v, BasePoint<Scalar, Scalar2> const& p)
{
  return {v.x + p.x, v.y + p.y};
}

template <typename Scalar, typename Scalar2>
constexpr BasePoint<Scalar, Scalar2> operator+(BasePoint<Scalar, Scalar2> const& p, BaseVector<Scalar, Scalar2> const& v)
{
  return {v.x + p.x, v.y + p.y};
}

template <typename Scalar, typename Scalar2>
constexpr bool operator==(BaseVector<Scalar, Scalar2> const& v1, BaseVector<Scalar, Scalar2> const& v2)
{
  return v1.x == v2.x && v1.y == v2.y;
}

template <typename Scalar, typename Scalar2>
constexpr bool operator!=(BaseVector<Scalar, Scalar2> const& v1, BaseVector<Scalar, Scalar2> const& v2)
{
  return v1.x != v2.x || v1.y != v2.y;
}

template <typename Scalar, typename Scalar2>
constexpr bool same_direction(BaseVector<Scalar, Scalar2> const& v1, BaseVector<Scalar, Scalar2> const& v2)
{
  return v1.quadrant() == v2.quadrant() && v1 % v2 == 0;
}

template <typename Scalar, typename Scalar2=Scalar>
struct BaseLine {
  Scalar a;
  Scalar b;
  Scalar c;

  constexpr BaseLine(Scalar a_, Scalar b_, Scalar c_): a{a_}, b{b_}, c{c_}
  {
  }

  template <typename OtherScalar, typename OtherScalar2>
  constexpr BaseLine(BaseLine<OtherScalar, OtherScalar2> const& l): a(l.a), b(l.b), c(l.c)
  {
  }

  constexpr static BaseLine of_direction(BaseVector<Scalar, Scalar2> const& v)
  {
    return {-v.y, v.x, 0};
  }

  constexpr static BaseLine through(BasePoint<Scalar, Scalar2> const& p1, BasePoint<Scalar, Scalar2> const& p2)
  {
    return BaseLine::of_direction(p2 - p1).parallel_through(p1);
  }

  constexpr BaseVector<Scalar, Scalar2> direction() const
  {
    return {-b, a};
  }

  constexpr BaseVector<Scalar, Scalar2> normal() const
  {
    return {a, b};
  }

  constexpr BaseLine parallel_through(BasePoint<Scalar, Scalar2> const& p) const
  {
    return BaseLine{a, b, -(a * p.x + b * p.y)};
  }

  constexpr BaseLine operator+() const
  {
    return *this;
  }

  constexpr BaseLine operator-() const
  {
    return BaseLine{-a, -b, -c};
  }

  constexpr Scalar value_at(BasePoint<Scalar, Scalar2> const& p)
  {
    return a * p.x + b * p.y + c;
  }
};

using FloatPoint = BasePoint<long double>;
using FloatVector = BaseVector<long double>;
using FloatLine = BaseLine<long double>;
using Point = BasePoint<int, long long>;
using Vector = BaseVector<int, long long>;
using Line = BaseLine<int, long long>;

FloatPoint intersection(FloatLine const& l1, FloatLine const& l2)
{
  auto den = l1.b * l2.a - l1.a * l2.b;
  return {(l1.c * l2.b - l1.b * l2.c) / den, (l1.a * l2.c - l1.c * l2.a) / den};
}

template <typename Scalar, typename Scalar2>
constexpr bool same_direction(BaseLine<Scalar, Scalar2> const& l1, BaseLine<Scalar, Scalar2> const& l2)
{
  return same_direction(l1.direction(), l2.direction());
}

struct Tower: Point {
  int magician;

  constexpr Tower(int x_, int y_, int m): Point(x_, y_), magician{m}
  {
  }
};

constexpr bool operator==(Tower const& t1, Tower const& t2)
{
  return t1.x == t2.x && t1.y == t2.y && t1.magician == t2.magician;
}

constexpr bool operator!=(Tower const& t1, Tower const& t2)
{
  return t1.x != t2.x || t1.y != t2.y || t1.magician != t2.magician;
}

bool above_intersection(Line const& line, Line const& l1, Line const& l2)
{
  auto den = l1.b * l2.a - l1.a * l2.b;
  if (den == 0) return true;
  auto x = l1.c * l2.b - l1.b * l2.c;
  auto y = l1.a * l2.c - l1.c * l2.a;
  using LL = long long;
  if (den > 0) return LL{line.a} * x + LL{line.b} * y + LL{line.c} * den >= 0;
  else return LL{line.a} * x + LL{line.b} * y + LL{line.c} * den <= 0;
}

vector<Line> intersect_halfplanes(vector<Line> lines)
{
  int n = lines.size();
  sort(lines.begin(), lines.end(), [&](Line const& l1, Line const& l2) {
    auto v1 = l1.direction();
    auto v2 = l2.direction();
    auto q1 = v1.quadrant();
    auto q2 = v2.quadrant();
    if (q1 != q2) return q1 < q2;
    auto p = v1 % v2;
    if (p != 0) return p > 0;
    Line arb{1, 0, 0};
    if (same_direction(l1, arb) || same_direction(l1, -arb)) arb = Line{0, 1, 0};
    return above_intersection(l1, l2, arb) && !above_intersection(l2, l1, arb);
  });
  vector<Line const*> queue(n);
  int b = 0;
  int e = 0;
  for (auto const& line: lines) {
    if (e > b && same_direction(line, *queue[e - 1])) continue;
    while (e - b >= 2 && above_intersection(line, *queue[e - 2], *queue[e - 1])) {
      --e;
    }
    while (e - b >= 2 && above_intersection(line, *queue[b], *queue[b + 1])) {
      ++b;
    }
    queue[e] = &line;
    ++e;
  }
  while (e - b >= 2 && above_intersection(*queue[b], *queue[e - 2], *queue[e - 1])) {
    --e;
  }
  vector<Line> res; res.reserve(e - b);
  for (int i = b; i < e; ++i) {
    res.emplace_back(*queue[i]);
  }
  return res;
}

long double triangle_area(FloatPoint const& p1, FloatPoint const& p2, FloatPoint const& p3)
{
  return (p2 - p1) % (p3 - p1) / 2;
}

long double area(vector<Line> const& lines)
{
  int n = lines.size();
  if (n < 3) return 0;
  vector<FloatPoint> points; points.reserve(n);
  for (int i = 0, j = 1; i < n; ++i, ++j) {
    while (j >= n) j -= n;
    points.emplace_back(intersection(FloatLine(lines[i]), FloatLine(lines[j])));
  }
  long double res = 0;
  for (int i = 2; i < n; ++i) {
    res += triangle_area(points[0], points[i-1], points[i]);
  }
  return abs(res);
}

long double solve(vector<Tower> towers)
{
  int n = towers.size();
  int m = n / 2;

  vector<Line> lines;
  for (auto const& t1: towers) {
    for (auto const& t2: towers) {
      if (t1.magician == t2.magician) continue;
      auto line = Line::through(t1, t2);
      vector<int> cnt(m, 0);
      for (auto const& t: towers) {
        auto v = line.value_at(t);
        if (v > 0) {
          ++cnt[t.magician];
          if (cnt[t.magician] >= 2) {
            goto bad;
          }
        }
      }
      lines.emplace_back(move(line));
bad:;
    }
  }
  return area(intersect_halfplanes(move(lines)));
}

}

int main()
{
  iostream::sync_with_stdio(false);
  cin.tie(nullptr);

  int n;
  cin >> n;
  vector<Tower> towers; towers.reserve(2 * n);
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < 2; ++j) {
      int x, y;
      cin >> x >> y;
      towers.emplace_back(x, y, i);
    }
  }

  auto res = solve(move(towers));

  cout << fixed << setprecision(numeric_limits<decltype(res)>::max_digits10) << res << endl;

  return 0;
}