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#include <bits/stdc++.h>
// #pragma GCC optimize ("O3")
// #pragma GCC target ("sse4")
using namespace std;

typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int,int> PII;

#define REP(i,n) for(int i=0;i<(n);++i)
#define FOR(i,a,b) for (int i=(a); i<(b); ++i)
#define FORD(i,a,b) for (int i=(a)-1; i>=(b); --i)

#define pb push_back
#define mp make_pair
#define st first
#define nd second

typedef LL Int10;
typedef LL Int20;

struct Point {
  Int10 x, y;
};
Int20 operator*(const Point& a, const Point& b) {
  return a.x * b.x + a.y * b.y;
}
Int20 det(const Point& a, const Point& b) {
  return a.x * b.y - b.x * a.y;
}
Point operator-(const Point& a, const Point& b) {
  return {a.x - b.x, a.y - b.y};
}
Point cross(const Point& a) {
  return {-a.y, a.x};
}

struct HalfPlane {
  // p * a <= c
  Point p;
  Int20 c;
};

ostream& operator<<(ostream& o, const HalfPlane& h) {
  return o << h.p.x << "X" << (h.p.y < 0 ? "" : "+") <<h.p.y<<"Y <= "<<h.c;
}

struct Intersection {
  double x;
  double y;
};

Intersection line_intersection(const HalfPlane& a, const HalfPlane& b) {
  Int20 d = det(a.p, b.p);
  assert(d);

  Point p = cross({a.p.x * b.c - b.p.x * a.c, a.p.y * b.c - b.p.y * a.c});
  return {p.x * 1.0 / d, p.y * 1.0 / d};
}

Point towers[105][2];
const double EPS = 1e-10;

int main(int argc, char* argv[]) {
  int N;
  scanf("%d", &N);
  REP(i,N)REP(j,2) scanf("%lld%lld", &towers[i][j].x, &towers[i][j].y);

  vector<HalfPlane> upper, lower;
  double minX = -1e3, maxX = 1e3;
  REP(i,N)REP(j,N) if (i != j) REP(k,2)REP(l,2) {
    Point a = towers[i][k], b = towers[j][l];

    HalfPlane h;
    h.p = cross(b-a);
    h.c = -1e8;
    REP(m,N) {
      h.c = max(h.c, min(h.p * towers[m][0], h.p * towers[m][1]));
    }

    if (h.p.y == 0) {
      if (h.p.x > 0) maxX = min(maxX, h.c / (double)h.p.x);
      else minX = max(minX, h.c / (double)h.p.x);
    } else if (h.p.y > 0) upper.pb(h);
    else lower.pb(h);
  }

  if (minX + 1e-9 >= maxX) {
    printf("%0.15lf\n", 0.0);
    return 0;
  }

  auto compute_hull = [](vector<HalfPlane> half_planes) {
    sort(half_planes.begin(), half_planes.end(), [](const HalfPlane& h1, const HalfPlane& h2) { return det(h1.p, h2.p) < 0; });
    half_planes.erase(
      unique(half_planes.begin(), half_planes.end(), [](const HalfPlane& h1, const HalfPlane& h2) { return det(h1.p, h2.p) == 0; }),
      half_planes.end()
    );

    vector<HalfPlane> hull;
    // cout << "START " << endl;
    for (auto& h: half_planes) {
      // cout << h << endl;

      while (hull.size() > 1) {
        Intersection i = line_intersection(hull[hull.size() - 2], hull[hull.size() - 1]);
        if (i.x * h.p.x + i.y * h.p.y <= h.c) break;
        hull.pop_back();
      }
      hull.pb(h);
    }
    return hull;
  };

  vector<HalfPlane> upper_hull = compute_hull(upper);
  vector<HalfPlane> lower_hull = compute_hull(lower);
  reverse(lower_hull.begin(), lower_hull.end());

  vector<double> Xs = {minX, maxX};
  REP(i, (int)upper_hull.size() - 1) {
    double x = line_intersection(upper_hull[i], upper_hull[i+1]).x;
    if (x > minX && x < maxX) Xs.pb(x);
  }
  REP(i, (int)lower_hull.size() - 1) {
    double x = line_intersection(lower_hull[i], lower_hull[i+1]).x;
    if (x > minX && x < maxX) Xs.pb(x);
  }
  sort(Xs.begin(), Xs.end());
  vector<pair<double, double>> Ys;

  int uix = 0, lix = 0;
  for (auto x: Xs) {
    while (uix + 1 < upper_hull.size() && line_intersection(upper_hull[uix], upper_hull[uix+1]).x < x) ++uix;
    while (lix + 1 < lower_hull.size() && line_intersection(lower_hull[lix], lower_hull[lix+1]).x < x) ++lix;

    auto at_x = [](const HalfPlane& h, const double& x) {
      return (h.c - h.p.x * x) / h.p.y;
    };
    Ys.pb({at_x(lower_hull[lix], x), at_x(upper_hull[uix], x)});
  }

  double result = 0.0;
  REP(i, Xs.size() - 1) {
    double r1 = Ys[i].nd - Ys[i].st;
    double r2 = Ys[i+1].nd - Ys[i+1].st;
    double d = Xs[i+1] - Xs[i];

    if (fabs(d) <= 0.0) continue;
    if (r1 <= 0.0 && r2 <= 0.0) continue;
    else if (r1 < 0.0 && r2 >= 0.0) {
      d = d * r2 / (r2 - r1);
      result += d * r2 / 2;
    } else if (r1 >= 0.0 && r2 < 0.0) {
      d = d * r1 / (r1 - r2);
      result += d * r1 / 2;
    } else {
      result += (r1 + r2) * d / 2;
    }
    // printf("%lf %lf %lf %lf\n", r1, r2, d, result);
  }
  printf("%0.15lf\n", result);
}