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#include <bits/stdc++.h>

using namespace std;

typedef long double ld;

const ld pi = acos(-1);
const ld eps = 1e-12;

struct point_t {
  ld x, y;

  point_t(ld x = 0, ld y = 0): x(x), y(y) {
  }

  point_t operator + (const point_t &b) const {
    return point_t(x + b.x, y + b.y);
  }

  point_t operator - (const point_t &b) const {
    return point_t(x - b.x, y - b.y);
  }

  point_t operator * (const ld &b) const {
    return point_t(x * b, y * b);
  }

  ld operator * (const point_t &b) const {
    return x * b.y - y * b.x;
  }

  bool operator < (const point_t &b) const {
    return x < b.x || (x == b.x && y < b.y);
  }

  bool operator == (const point_t &b) const {
    return x == b.x && y == b.y;
  }

  bool operator != (const point_t &b) const {
    return x != b.x || y != b.y;
  }
};

struct line_t {
  point_t p, v;
  ld slope;

  line_t() {
  }

  line_t(point_t p, point_t v): p(p), v(v) {
    slope = atan2l(v.y, v.x);
  }

  bool operator < (const line_t &b) const {
    return slope < b.slope;
  }
};

template<typename T> inline int sign(const T &x) {
  return fabsl(x) < eps ? 0 : x > 0 ? 1 : -1;
}

bool on_left(const line_t &l, const point_t &p) {
  return sign(l.v * (p - l.p)) >= 0;
}

point_t intersect(const line_t &u, const line_t &v) {
  ld w = ((v.p - u.p) * v.v) / (u.v * v.v);
  return u.p + u.v * w;
}

ld semiplane(vector<line_t> l) {
  int n = l.size();
  sort(l.begin(), l.end());
  vector<line_t> q(n);
  vector<point_t> p(n);
  int ql = 0, qr = 0;
  q[0] = l[0];
  for (int i = 1; i < n; ++i) {
    while (ql < qr && !on_left(l[i], p[qr - 1])) {
      --qr;
    }
    while (ql < qr && !on_left(l[i], p[ql])) {
      ++ql;
    }
    if (!sign(l[i].v * q[qr].v)) {
      if (!on_left(l[i], q[qr].p)) {
        q[qr] = l[i];
      }
    } else {
      q[++qr] = l[i];
    }
    if (ql < qr) {
      p[qr - 1] = intersect(q[qr - 1], q[qr]);
    }
  }
  while (ql < qr && !on_left(q[ql], p[qr - 1])) {
    --qr;
  }
  if (ql + 1 >= qr) {
    return 0;
  }
  p[qr] = intersect(q[qr], q[ql]);
  ld answer = p[qr] * p[ql];
  for (int i = ql; i < qr; ++i) {
    answer += p[i] * p[i + 1];
  }
  if (answer < 0) {
    answer = 0;
  }
  return answer / 2;
}

int main() {
#ifdef wxh010910
  freopen("input.txt", "r", stdin);
#endif
  int n;
  scanf("%d", &n);
  vector<point_t> a(n), b(n);
  for (int i = 0; i < n; ++i) {
    int ax, ay, bx, by;
    scanf("%d %d %d %d", &ax, &ay, &bx, &by);
    a[i] = point_t(ax, ay);
    b[i] = point_t(bx, by);
  }
  vector<ld> angles;
  angles.push_back(0);
  angles.push_back(pi * 2);
  auto add = [&](point_t a, point_t b) {
    if (a == b) {
      return;
    }
    ld theta = atan2l(b.y - a.y, b.x - a.x) + pi / 2;
    while (theta < 0) {
      theta += pi * 2;
    }
    while (theta >= pi * 2) {
      theta -= pi * 2;
    }
    angles.push_back(theta);
    theta += pi;
    while (theta < 0) {
      theta += pi * 2;
    }
    while (theta >= pi * 2) {
      theta -= pi * 2;
    }
    angles.push_back(theta);
  };
  for (int i = 0; i < n; ++i) {
    for (int j = 0; j < i; ++j) {
      add(a[i], a[j]);
      add(a[i], b[j]);
      add(b[i], a[j]);
      add(b[i], b[j]);
    }
    add(a[i], b[i]);
  }
  sort(angles.begin(), angles.end());
  angles.erase(unique(angles.begin(), angles.end()), angles.end());
  vector<line_t> lines;
  auto solve = [&](ld theta) {
    theta = 2 * pi - theta;
    ld c = cosl(theta), s = sinl(theta);
    ld xmax = -1e9;
    point_t p(0, 0);
    for (int i = 0; i < n; ++i) {
      ld xa = a[i].x * c - a[i].y * s;
      ld xb = b[i].x * c - b[i].y * s;
      if (xa > xb) {
        if (xb > xmax) {
          xmax = xb;
          p = b[i];
        }
      } else {
        if (xa > xmax) {
          xmax = xa;
          p = a[i];
        }
      }
    }
    return p;
  };
  auto insert = [&](point_t p, ld theta) {
    lines.push_back(line_t(p, point_t(cosl(theta + pi / 2), sinl(theta + pi / 2))));
  };
  for (int i = 0; i < angles.size() - 1; ++i) {
    point_t p = solve((angles[i] + angles[i + 1]) / 2);
    insert(p, angles[i]);
    insert(p, angles[i + 1]);
  }
  printf("%.10lf\n", (double)(semiplane(lines) + eps));
  return 0;
}