Problem p01633 (C++) — buggy submission, verdict: Runtime Error

#include <bits/stdc++.h>

#define REP(i, s, n) for (int i = s; i < n; i++)
#define rep(i, n) REP(i, 0, n)
#define EPS (1e-6)
#define equals(a, b) (fabs((a) - (b)) < EPS)
#define COUNTER_CLOCKWISE 1
#define CLOCKWISE -1
#define ONLINE_BACK 2
#define ONLINE_FRONT -2
#define ON_SEGMENT 0

using namespace std;

class Point {
public:
  double x, y;

  Point(double x = 0, double y = 0) : x(x), y(y) {}

  Point operator+(Point p) { return Point(x + p.x, y + p.y); }
  Point operator-(Point p) { return Point(x - p.x, y - p.y); }
  Point operator*(double a) { return Point(a * x, a * y); }
  Point operator/(double a) { return Point(x / a, y / a); }
  Point operator*(Point a) {
    return Point(x * a.x - y * a.y, x * a.y + y * a.x);
  }

  bool operator<(const Point &p) const {
    return !equals(x, p.x) ? x < p.x : (!equals(y, p.y) && y < p.y);
  }

  bool operator==(const Point &p) const {
    return fabs(x - p.x) < EPS && fabs(y - p.y) < EPS;
  }
};

struct Segment {
  Point p1, p2;
  Segment(Point p1 = Point(), Point p2 = Point()) : p1(p1), p2(p2) {}
  bool operator<(const Segment &s) const {
    return (p2 == s.p2) ? p1 < s.p1 : p2 < s.p2;
  }
  bool operator==(const Segment &s) const {
    return (s.p1 == p1 && s.p2 == p2) || (s.p1 == p2 && s.p2 == p1);
  }
};

typedef Point Vector;
typedef Segment Line;
typedef vector<Point> Polygon;

ostream &operator<<(ostream &os, const Point &a) {
  os << "(" << a.x << "," << a.y << ")";
}

ostream &operator<<(ostream &os, const Segment &a) {
  os << "( " << a.p1 << " , " << a.p2 << " )";
}

double dot(Point a, Point b) { return a.x * b.x + a.y * b.y; }

double cross(Point a, Point b) { return a.x * b.y - a.y * b.x; }

double norm(Point a) { return a.x * a.x + a.y * a.y; }

double abs(Point a) { return sqrt(norm(a)); }

int ccw(Point p0, Point p1, Point p2) {
  Point a = p1 - p0;
  Point b = p2 - p0;
  if (cross(a, b) > EPS)
    return COUNTER_CLOCKWISE;
  if (cross(a, b) < -EPS)
    return CLOCKWISE;
  if (dot(a, b) < -EPS)
    return ONLINE_BACK;
  if (norm(a) < norm(b))
    return ONLINE_FRONT;
  return ON_SEGMENT;
}

bool intersectLL(Line l, Line m) {
  return abs(cross(l.p2 - l.p1, m.p2 - m.p1)) > EPS || // non-parallel
         abs(cross(l.p2 - l.p1, m.p1 - l.p1)) < EPS;   // same line
}
bool intersectLS(Line l, Line s) {
  return cross(l.p2 - l.p1, s.p1 - l.p1) * // s[0] is left of l
             cross(l.p2 - l.p1, s.p2 - l.p1) <
         EPS; // s[1] is right of l
}
bool intersectLP(Line l, Point p) {
  return abs(cross(l.p2 - p, l.p1 - p)) < EPS;
}
bool intersectSS(Line s, Line t) {
  return ccw(s.p1, s.p2, t.p1) * ccw(s.p1, s.p2, t.p2) <= 0 &&
         ccw(t.p1, t.p2, s.p1) * ccw(t.p1, t.p2, s.p2) <= 0;
}
bool intersectSP(Line s, Point p) {
  return abs(s.p1 - p) + abs(s.p2 - p) - abs(s.p2 - s.p1) <
         EPS; // triangle inequality
}

Point projection(Line l, Point p) {
  double t = dot(p - l.p1, l.p1 - l.p2) / norm(l.p1 - l.p2);
  return l.p1 + (l.p1 - l.p2) * t;
}
Point reflection(Line l, Point p) { return p + (projection(l, p) - p) * 2; }
double distanceLP(Line l, Point p) { return abs(p - projection(l, p)); }
double distanceLL(Line l, Line m) {
  return intersectLL(l, m) ? 0 : distanceLP(l, m.p1);
}

double distanceLS(Line l, Line s) {
  if (intersectLS(l, s))
    return 0;
  return min(distanceLP(l, s.p1), distanceLP(l, s.p2));
}
double distanceSP(Line s, Point p) {
  Point r = projection(s, p);
  if (intersectSP(s, r))
    return abs(r - p);
  return min(abs(s.p1 - p), abs(s.p2 - p));
}

double distanceSS(Line s, Line t) {
  if (intersectSS(s, t))
    return 0;
  return min(min(distanceSP(s, t.p1), distanceSP(s, t.p2)),
             min(distanceSP(t, s.p1), distanceSP(t, s.p2)));
}

Point crosspoint(Line l, Line m) {
  double A = cross(l.p2 - l.p1, m.p2 - m.p1);
  double B = cross(l.p2 - l.p1, l.p2 - m.p1);
  if (abs(A) < EPS && abs(B) < EPS) {
    vector<Point> vec;
    vec.push_back(l.p1), vec.push_back(l.p2), vec.push_back(m.p1),
        vec.push_back(m.p2);
    sort(vec.begin(), vec.end());
    assert(vec[1] == vec[2]); // 同じセグメントかもよ
    return vec[1];
    // return m.p1;
  }
  if (abs(A) < EPS)
    assert(false);
  return m.p1 + (m.p2 - m.p1) * (B / A);
}

// cross product of pq and pr
double cross3p(Point p, Point q, Point r) {
  return (r.x - q.x) * (p.y - q.y) - (r.y - q.y) * (p.x - q.x);
}

// returns true if point r is on the same line as the line pq
bool collinear(Point p, Point q, Point r) {
  return fabs(cross3p(p, q, r)) < EPS;
}

// returns true if point t is on the left side of line pq
bool ccwtest(Point p, Point q, Point r) {
  return cross3p(p, q, r) > 0; // can be modified to accept collinear points
}

bool onSegment(Point p, Point q, Point r) {
  return collinear(p, q, r) &&
         equals(sqrt(pow(p.x - r.x, 2) + pow(p.y - r.y, 2)) +
                    sqrt(pow(r.x - q.x, 2) + pow(r.y - q.y, 2)),
                sqrt(pow(p.x - q.x, 2) + pow(p.y - q.y, 2)));
}

bool isConvex(vector<Point> p) {
  int sz = (int)p.size();
  if (sz < 3)
    return false; // boundary case, we treat a point or a line as not convex
  bool isLeft = ccwtest(p[0], p[1], p[2]);
  for (int i = 1; i < (int)p.size(); i++)
    if (ccwtest(p[i], p[(i + 1) % sz], p[(i + 2) % sz]) != isLeft)
      return false;
  return true;
}

double angle(Point a, Point b, Point c) {
  double ux = b.x - a.x, uy = b.y - a.y;
  double vx = c.x - a.x, vy = c.y - a.y;
  return acos((ux * vx + uy * vy) /
              sqrt((ux * ux + uy * uy) * (vx * vx + vy * vy)));
}

// 多角形poly内（線分上も含む）に点pが存在するかどうは判定する
bool inPolygon(Polygon poly, Point p) {
  if ((int)poly.size() == 0)
    return false;
  rep(i, poly.size()) if (onSegment(poly[i], poly[(i + 1) % poly.size()],
                                    p)) return true;
  double sum = 0;
  for (int i = 0; i < (int)poly.size(); i++) {
    if (equals(cross(poly[i] - p, poly[(i + 1) % poly.size()] - p), 0.0))
      continue; // ３点が平行だとangleがnanを返しsumがnanになり死ぬ
    if (cross3p(p, poly[i], poly[(i + 1) % poly.size()]) < 0)
      sum -= angle(p, poly[i], poly[(i + 1) % poly.size()]);
    else
      sum += angle(p, poly[i], poly[(i + 1) % poly.size()]);
  }
  // あまり誤差を厳しくしすぎると良くないので以下のほうが良い
  const double eps = 1e-5;
  return (fabs(sum - 2 * M_PI) < eps || fabs(sum + 2 * M_PI) < eps);
}

struct Edge {
  int from, to, rev;
  double cost;
  Edge(int from = 0, int to = 0, int rev = -1, double cost = 0)
      : from(from), to(to), rev(rev), cost(cost) {}
  bool operator<(const Edge &a) const {
    return !equals(cost, a.cost) && cost < a.cost;
  }
};

vector<vector<Edge>> segmentArrangement(vector<Segment> vs, vector<Point> &ps) {

  rep(i, vs.size()) REP(j, i + 1, vs.size()) if (intersectSS(vs[i], vs[j]))
      ps.push_back(Point(crosspoint(vs[i], vs[j])));

  sort(ps.begin(), ps.end());
  ps.erase(unique(ps.begin(), ps.end()), ps.end());

  vector<vector<Edge>> ret(ps.size());

  for (int i = 0; i < vs.size(); i++) {
    vector<pair<double, int>> list;
    rep(j, ps.size()) if (intersectSP(vs[i], ps[j]))
        list.push_back(pair<double, int>(norm(vs[i].p1 - ps[j]), j));
    sort(list.begin(), list.end());
    for (int j = 0; j + 1 < list.size(); ++j) {
      int from = list[j].second, to = list[j + 1].second;
      double cost = abs(ps[from] - ps[to]);
      ret[from].push_back(Edge(from, to, -1, cost));
      ret[to].push_back(Edge(to, from, -1, cost));
    }
  }

  vector<Point> tmp;
  rep(i, ps.size()) if (ret[i].size() >= 2) tmp.push_back(ps[i]);
  ps = tmp;
  ret.clear();
  ret.resize(ps.size());
  for (int i = 0; i < vs.size(); i++) {
    vector<pair<double, int>> list;
    rep(j, ps.size()) if (intersectSP(vs[i], ps[j]))
        list.push_back(pair<double, int>(norm(vs[i].p1 - ps[j]), j));
    sort(list.begin(), list.end());
    for (int j = 0; j + 1 < list.size(); ++j) {
      int from = list[j].second, to = list[j + 1].second;
      double cost = abs(ps[from] - ps[to]);
      ret[from].push_back(Edge(from, to, -1, cost));
      ret[to].push_back(Edge(to, from, -1, cost));
    }
  }

  return ret;
}

////////////////// にゃんこまっしぐら ///////////////////////////////
const int MAX_V = 5000;
bool visited[MAX_V][MAX_V];
vector<vector<Edge>> G;
vector<Point> vp;

bool getPath(int start_node, int node, int edge, vector<Point> &buf,
             set<Point> &used) {
  if (visited[node][edge]) {
    if (!buf.empty() && node == start_node)
      return true;
    return false;
  }
  visited[node][edge] = true;
  if (used.count(vp[node]))
    return visited[node][edge] = false;
  used.insert(vp[node]);
  int next_node = G[node][edge].to;
  int next_edge = (G[node][edge].rev + 1) % ((int)G[next_node].size());
  buf.push_back(vp[G[node][edge].from]);
  if (getPath(start_node, next_node, next_edge, buf, used))
    return true;
  else
    return visited[node][edge] = false;
}
///////////////// みゃおみゃお //////////////////////////////////////

int uf[MAX_V];
void init(int _size = MAX_V) { rep(i, _size) uf[i] = i; }
int find(int x) {
  if (x == uf[x])
    return x;
  return uf[x] = find(uf[x]);
}
void unit(int x, int y) {
  x = find(x), y = find(y);
  if (x != y)
    uf[x] = y;
}

bool LT(double a, double b) { return !equals(a, b) && a < b; }
bool LTE(double a, double b) { return equals(a, b) || a < b; }

// true -> CCW, false -> CW
bool rotationCheck(vector<Point> &vec) {
  double sum = 0;
  for (int i = 0; i < vec.size(); i++)
    sum += cross(vec[i], vec[(i + 1) % vec.size()]);
  return (!equals(sum, 0.0) && sum > 0);
}

Point vir;
bool comp_angle(const Edge &a, const Edge &b) {
  Vector va = vir - vp[a.to];
  Vector vb = vir - vp[b.to];
  return LT(atan2(va.y, va.x), atan2(vb.y, vb.x));
}

bool inPolygon(Polygon a, Polygon b) {
  rep(i, (int)a.size()) {
    Point mp = (a[i] + a[(i + 1) % (int)a.size()]) / 2.0;
    if (!inPolygon(b, mp))
      return false;
  }
  return true;
}

bool canUnit(Polygon a, Polygon b) {
  if (inPolygon(a, b) || inPolygon(b, a))
    return true;
  rep(i, (int)a.size()) rep(j, (int)b.size()) {
    Segment seg_a = Segment(a[i], a[(i + 1) % (int)a.size()]);
    Segment seg_b = Segment(b[j], b[(j + 1) % (int)b.size()]);
    if (equals(cross(seg_a.p1 - seg_a.p2, seg_b.p1 - seg_b.p2), 0.0)) {
      if (onSegment(seg_a.p1, seg_a.p2, seg_b.p1) ||
          onSegment(seg_a.p1, seg_a.p2, seg_b.p2) ||
          onSegment(seg_b.p1, seg_b.p2, seg_a.p1) ||
          onSegment(seg_b.p1, seg_b.p2, seg_a.p2)) {
        vector<Point> tmp;
        tmp.push_back(seg_a.p1), tmp.push_back(seg_a.p2);
        tmp.push_back(seg_b.p1), tmp.push_back(seg_b.p2);
        sort(tmp.begin(), tmp.end());
        if (tmp[1] == tmp[2])
          continue;
        return true;
      }
    }
  }
  rep(i, (int)a.size()) {
    Point mp = (a[i] + a[(i + 1) % (int)a.size()]) / 2.0;
    if (inPolygon(b, mp))
      return true;
  }
  rep(i, (int)b.size()) {
    Point mp = (b[i] + b[(i + 1) % (int)b.size()]) / 2.0;
    if (inPolygon(a, mp))
      return true;
  }
  return false;
}

int N;

void compute(vector<Segment> &segs) {
  G = segmentArrangement(segs, vp);
  int V = G.size();
  /*
  cout << V << endl;
  rep(i,V) cout << vp[i] << endl;
  */
  assert(V < MAX_V);

  rep(i, V) {
    vir = vp[i];
    sort(G[i].begin(), G[i].end(), comp_angle);
  }

  rep(i, V) rep(j, (int)G[i].size()) if (G[i][j].rev == -1) {
    int to = G[i][j].to;
    rep(k, (int)G[to].size()) if (G[to][k].to == i) {
      G[i][j].rev = k;
      G[to][k].rev = j;
      break;
    }
  }

  vector<Polygon> polies;
  rep(i, V) rep(j, (int)G[i].size()) if (!visited[i][j]) {
    vector<Point> buf;
    set<Point> used;
    if (getPath(i, i, j, buf, used))
      if ((int)buf.size() >= 3) {
        polies.push_back(buf);
      }
  }
  V = polies.size();
  /*
  cout << V << endl;
  rep(i,V){
    cout << i << "-th:" << endl;
    rep(j,polies[i].size()) cout << polies[i][j] << " "; cout << endl;
  }

  cout << endl;
  cout << endl;
  rep(i,V){
    rep(j,polies[i].size()){
      cout << polies[i][j].x << " " << polies[i][j].y << " " <<
  polies[i][(j+1)%polies[i].size()].x << " " <<
  polies[i][(j+1)%polies[i].size()].y << endl;
    }
  }
  cout << endl;
  cout << endl;
  */
  init(V);
  set<int> S;
  rep(i, V) rep(j, V) if (i != j) {
    if (canUnit(polies[i], polies[j]))
      unit(i, j);
  }
  rep(i, V) S.insert(find(i));
  cout << (int)S.size() << endl;
}

int main() {
  cin >> N;
  vector<Segment> segs(N);
  rep(i, N) cin >> segs[i].p1.x >> segs[i].p1.y >> segs[i].p2.x >> segs[i].p2.y;
  compute(segs);
  return 0;
}

Error: 0

Fixed submission:

#include <bits/stdc++.h>

#define REP(i, s, n) for (int i = s; i < n; i++)
#define rep(i, n) REP(i, 0, n)
#define EPS (1e-4)
#define equals(a, b) (fabs((a) - (b)) < EPS)
#define COUNTER_CLOCKWISE 1
#define CLOCKWISE -1
#define ONLINE_BACK 2
#define ONLINE_FRONT -2
#define ON_SEGMENT 0

using namespace std;

class Point {
public:
  double x, y;

  Point(double x = 0, double y = 0) : x(x), y(y) {}

  Point operator+(Point p) { return Point(x + p.x, y + p.y); }
  Point operator-(Point p) { return Point(x - p.x, y - p.y); }
  Point operator*(double a) { return Point(a * x, a * y); }
  Point operator/(double a) { return Point(x / a, y / a); }
  Point operator*(Point a) {
    return Point(x * a.x - y * a.y, x * a.y + y * a.x);
  }

  bool operator<(const Point &p) const {
    return !equals(x, p.x) ? x < p.x : (!equals(y, p.y) && y < p.y);
  }

  bool operator==(const Point &p) const {
    return fabs(x - p.x) < EPS && fabs(y - p.y) < EPS;
  }
};

struct Segment {
  Point p1, p2;
  Segment(Point p1 = Point(), Point p2 = Point()) : p1(p1), p2(p2) {}
  bool operator<(const Segment &s) const {
    return (p2 == s.p2) ? p1 < s.p1 : p2 < s.p2;
  }
  bool operator==(const Segment &s) const {
    return (s.p1 == p1 && s.p2 == p2) || (s.p1 == p2 && s.p2 == p1);
  }
};

typedef Point Vector;
typedef Segment Line;
typedef vector<Point> Polygon;

ostream &operator<<(ostream &os, const Point &a) {
  os << "(" << a.x << "," << a.y << ")";
}

ostream &operator<<(ostream &os, const Segment &a) {
  os << "( " << a.p1 << " , " << a.p2 << " )";
}

double dot(Point a, Point b) { return a.x * b.x + a.y * b.y; }

double cross(Point a, Point b) { return a.x * b.y - a.y * b.x; }

double norm(Point a) { return a.x * a.x + a.y * a.y; }

double abs(Point a) { return sqrt(norm(a)); }

int ccw(Point p0, Point p1, Point p2) {
  Point a = p1 - p0;
  Point b = p2 - p0;
  if (cross(a, b) > EPS)
    return COUNTER_CLOCKWISE;
  if (cross(a, b) < -EPS)
    return CLOCKWISE;
  if (dot(a, b) < -EPS)
    return ONLINE_BACK;
  if (norm(a) < norm(b))
    return ONLINE_FRONT;
  return ON_SEGMENT;
}

bool intersectLL(Line l, Line m) {
  return abs(cross(l.p2 - l.p1, m.p2 - m.p1)) > EPS || // non-parallel
         abs(cross(l.p2 - l.p1, m.p1 - l.p1)) < EPS;   // same line
}
bool intersectLS(Line l, Line s) {
  return cross(l.p2 - l.p1, s.p1 - l.p1) * // s[0] is left of l
             cross(l.p2 - l.p1, s.p2 - l.p1) <
         EPS; // s[1] is right of l
}
bool intersectLP(Line l, Point p) {
  return abs(cross(l.p2 - p, l.p1 - p)) < EPS;
}
bool intersectSS(Line s, Line t) {
  return ccw(s.p1, s.p2, t.p1) * ccw(s.p1, s.p2, t.p2) <= 0 &&
         ccw(t.p1, t.p2, s.p1) * ccw(t.p1, t.p2, s.p2) <= 0;
}
bool intersectSP(Line s, Point p) {
  return abs(s.p1 - p) + abs(s.p2 - p) - abs(s.p2 - s.p1) <
         EPS; // triangle inequality
}

Point projection(Line l, Point p) {
  double t = dot(p - l.p1, l.p1 - l.p2) / norm(l.p1 - l.p2);
  return l.p1 + (l.p1 - l.p2) * t;
}
Point reflection(Line l, Point p) { return p + (projection(l, p) - p) * 2; }
double distanceLP(Line l, Point p) { return abs(p - projection(l, p)); }
double distanceLL(Line l, Line m) {
  return intersectLL(l, m) ? 0 : distanceLP(l, m.p1);
}

double distanceLS(Line l, Line s) {
  if (intersectLS(l, s))
    return 0;
  return min(distanceLP(l, s.p1), distanceLP(l, s.p2));
}
double distanceSP(Line s, Point p) {
  Point r = projection(s, p);
  if (intersectSP(s, r))
    return abs(r - p);
  return min(abs(s.p1 - p), abs(s.p2 - p));
}

double distanceSS(Line s, Line t) {
  if (intersectSS(s, t))
    return 0;
  return min(min(distanceSP(s, t.p1), distanceSP(s, t.p2)),
             min(distanceSP(t, s.p1), distanceSP(t, s.p2)));
}

Point crosspoint(Line l, Line m) {
  double A = cross(l.p2 - l.p1, m.p2 - m.p1);
  double B = cross(l.p2 - l.p1, l.p2 - m.p1);
  if (abs(A) < EPS && abs(B) < EPS) {
    vector<Point> vec;
    vec.push_back(l.p1), vec.push_back(l.p2), vec.push_back(m.p1),
        vec.push_back(m.p2);
    sort(vec.begin(), vec.end());
    assert(vec[1] == vec[2]); // 同じセグメントかもよ
    return vec[1];
    // return m.p1;
  }
  if (abs(A) < EPS)
    assert(false);
  return m.p1 + (m.p2 - m.p1) * (B / A);
}

// cross product of pq and pr
double cross3p(Point p, Point q, Point r) {
  return (r.x - q.x) * (p.y - q.y) - (r.y - q.y) * (p.x - q.x);
}

// returns true if point r is on the same line as the line pq
bool collinear(Point p, Point q, Point r) {
  return fabs(cross3p(p, q, r)) < EPS;
}

// returns true if point t is on the left side of line pq
bool ccwtest(Point p, Point q, Point r) {
  return cross3p(p, q, r) > 0; // can be modified to accept collinear points
}

bool onSegment(Point p, Point q, Point r) {
  return collinear(p, q, r) &&
         equals(sqrt(pow(p.x - r.x, 2) + pow(p.y - r.y, 2)) +
                    sqrt(pow(r.x - q.x, 2) + pow(r.y - q.y, 2)),
                sqrt(pow(p.x - q.x, 2) + pow(p.y - q.y, 2)));
}

bool isConvex(vector<Point> p) {
  int sz = (int)p.size();
  if (sz < 3)
    return false; // boundary case, we treat a point or a line as not convex
  bool isLeft = ccwtest(p[0], p[1], p[2]);
  for (int i = 1; i < (int)p.size(); i++)
    if (ccwtest(p[i], p[(i + 1) % sz], p[(i + 2) % sz]) != isLeft)
      return false;
  return true;
}

double angle(Point a, Point b, Point c) {
  double ux = b.x - a.x, uy = b.y - a.y;
  double vx = c.x - a.x, vy = c.y - a.y;
  return acos((ux * vx + uy * vy) /
              sqrt((ux * ux + uy * uy) * (vx * vx + vy * vy)));
}

// 多角形poly内（線分上も含む）に点pが存在するかどうは判定する
bool inPolygon(Polygon poly, Point p) {
  if ((int)poly.size() == 0)
    return false;
  rep(i, poly.size()) if (onSegment(poly[i], poly[(i + 1) % poly.size()],
                                    p)) return true;
  double sum = 0;
  for (int i = 0; i < (int)poly.size(); i++) {
    if (equals(cross(poly[i] - p, poly[(i + 1) % poly.size()] - p), 0.0))
      continue; // ３点が平行だとangleがnanを返しsumがnanになり死ぬ
    if (cross3p(p, poly[i], poly[(i + 1) % poly.size()]) < 0)
      sum -= angle(p, poly[i], poly[(i + 1) % poly.size()]);
    else
      sum += angle(p, poly[i], poly[(i + 1) % poly.size()]);
  }
  // あまり誤差を厳しくしすぎると良くないので以下のほうが良い
  const double eps = 1e-5;
  return (fabs(sum - 2 * M_PI) < eps || fabs(sum + 2 * M_PI) < eps);
}

struct Edge {
  int from, to, rev;
  double cost;
  Edge(int from = 0, int to = 0, int rev = 0, double cost = 0)
      : from(from), to(to), rev(rev), cost(cost) {}
  bool operator<(const Edge &a) const {
    return !equals(cost, a.cost) && cost < a.cost;
  }
};

vector<vector<Edge>> segmentArrangement(vector<Segment> vs, vector<Point> &ps) {

  rep(i, vs.size()) REP(j, i + 1, vs.size()) {
    if (intersectSS(vs[i], vs[j])) {
      ps.push_back(Point(crosspoint(vs[i], vs[j])));
    }
  }

  sort(ps.begin(), ps.end());
  ps.erase(unique(ps.begin(), ps.end()), ps.end());

  vector<vector<Edge>> ret(ps.size());

  for (int i = 0; i < vs.size(); i++) {
    vector<pair<double, int>> list;
    rep(j, ps.size()) if (intersectSP(vs[i], ps[j]))
        list.push_back(pair<double, int>(norm(vs[i].p1 - ps[j]), j));
    sort(list.begin(), list.end());
    for (int j = 0; j + 1 < list.size(); ++j) {
      int from = list[j].second, to = list[j + 1].second;
      double cost = abs(ps[from] - ps[to]);
      ret[from].push_back(Edge(from, to, -1, cost));
      ret[to].push_back(Edge(to, from, -1, cost));
    }
  }
  return ret;
}

///////////// にゃんこまっしぐら ////////////////////////
vector<vector<Edge>> G;
vector<Point> vp;
const int MAX_V = 8000;
bool visited[MAX_V][MAX_V];

bool getPath(int start_node, int node, int edge, vector<Point> &buf,
             set<Point> &S) {
  if (visited[node][edge]) {
    if (!buf.empty() && node == start_node)
      return true;
    return false;
  }
  visited[node][edge] = true;

  int next_node = G[node][edge].to;
  int next_edge = (G[node][edge].rev + 1) % ((int)G[next_node].size());
  if (S.count(vp[G[next_node][next_edge].from]))
    return visited[node][edge] = false;
  S.insert(vp[G[next_node][next_edge].from]);
  buf.push_back(vp[G[node][edge].from]);
  if (getPath(start_node, next_node, next_edge, buf, S))
    return true;
  else
    return visited[node][edge] = false;
}
///////////// にゃんにゃん ////////////////////////////////

bool inPolygon(Polygon a, Polygon b) {
  rep(i, (int)b.size()) {
    Point mp = (b[i] + b[(i + 1) % (int)b.size()]) / 2.0;
    if (!inPolygon(a, mp))
      return false;
  }
  return true;
}

bool canUnit(Polygon a, Polygon b) {
  if (inPolygon(a, b) || inPolygon(b, a))
    return true;
  rep(i, (int)a.size()) {
    rep(j, (int)b.size()) {
      if ((onSegment(a[i], a[(i + 1) % (int)a.size()], b[j]) &&
           onSegment(a[i], a[(i + 1) % (int)a.size()],
                     b[(j + 1) % (int)b.size()])) ||
          (onSegment(b[j], b[(j + 1) % (int)b.size()], a[i]) &&
           onSegment(b[j], b[(j + 1) % (int)b.size()],
                     a[(i + 1) % (int)a.size()])))
        return true;
      if (intersectSS(Segment(a[i], a[(i + 1) % (int)a.size()]),
                      Segment(b[j], b[(j + 1) % (int)b.size()]))) {
        Point cp = crosspoint(Segment(a[i], a[(i + 1) % (int)a.size()]),
                              Segment(b[j], b[(j + 1) % (int)b.size()]));
        if (cp == a[i] || cp == a[(i + 1) % (int)a.size()] || cp == b[j] ||
            cp == b[(j + 1) % (int)b.size()])
          continue;
        return true;
      }
    }
  }
  return false;
}

int N;
vector<Segment> segs;

bool LT(double a, double b) { return !equals(a, b) && a < b; }

Point vir;
bool comp_angle(Edge a, Edge b) {
  Vector va = vir - vp[a.to];
  Vector vb = vir - vp[b.to];
  return LT(atan2(va.y, va.x), atan2(vb.y, vb.x));
}

int uf[MAX_V];

int find(int x) {
  if (x == uf[x])
    return x;
  return uf[x] = find(uf[x]);
}

void unit(int x, int y) {
  x = find(x), y = find(y);
  if (x != y)
    uf[x] = y;
}

void init(int _size = MAX_V) { rep(i, _size) uf[i] = i; }

void compute() {
  G = segmentArrangement(segs, vp);

  int V = vp.size();
  assert(V < MAX_V);
  rep(i, V) {
    vir = vp[i];
    sort(G[i].begin(), G[i].end(), comp_angle);
  }
  rep(i, V) rep(j, G[i].size()) if (G[i][j].rev == -1) {
    int to = G[i][j].to;
    rep(k, G[to].size()) if (G[to][k].to == i) {
      G[i][j].rev = k;
      G[to][k].rev = j;
      break;
    }
  }

  vector<Polygon> poly;
  rep(i, V) rep(j, G[i].size()) {
    Polygon buf;
    set<Point> S;
    if (getPath(i, i, j, buf, S)) {
      if (buf.size() >= 3)
        poly.push_back(buf);
    }
  }
  /*
  cout << endl;
  rep(i,poly.size()){
    cout << i << "-th" << endl;
    rep(j,poly[i].size()) cout << poly[i][j] << " "; cout << endl;
  }
  */
  V = poly.size();
  assert(V < MAX_V);
  init(V);
  rep(i, V) rep(j, V) if (i != j && canUnit(poly[i], poly[j])) unit(i, j);
  set<int> S;
  rep(i, V) S.insert(find(i));
  // rep(i,V) cout << i << "-th : " << find(i) << endl;
  cout << (int)S.size() << endl;
}

int main() {
  cin >> N;
  segs.resize(N);
  rep(i, N) cin >> segs[i].p1.x >> segs[i].p1.y >> segs[i].p2.x >> segs[i].p2.y;
  compute();
  return 0;
}