Problem: In Medieval times existed the tradition of burning witches at steaks together with their pets, black cats. By the end of the 15-th century the population of black cats ceased to exist. The difficulty of the situation led to creating the EIC - the Emergency Inquisitory Commission.

The resolution #666 says that a white cat is considered black when and only when the perimeter of its black spots exceeds the acceptable norm. But what does the acceptable norm equal to? Every inquisitor will choose it himself depending on the situation. And your task is to find the perimeter of black spots on the cat's fur.

The very same resolution says that the cat's fur is a white square with the length of 105. During the measurement of spots it is customary to put the lower left corner of the fur into the origin of axes (0;0) and the upper right one — to the point with coordinates (105;105). The cats' spots are nondegenerate triangles. The spots can intersect and overlap with each other, but it is guaranteed that each pair of the triangular spots' sides have no more than one common point.

We'll regard the perimeter in this problem as the total length of the boarders where a cat's fur changes color.

Input

The first input line contains a single integer n (0 ≤ n ≤ 100). It is the number of spots on the cat's fur. The i-th of the last n lines contains 6 integers: x1i, y1i, x2i, y2i, x3i, y3i. They are the coordinates of the i-th triangular spot (0 < xji, yji < 105).

Output

Print a single number, the answer to the problem, perimeter of the union of triangles. Your answer should differ from the correct one in no more than 10 - 6.

Examples

Input

1
1 1 2 1 1 2


Output

3.4142135624


Input

3
3 3 10 3 3 10
1 1 9 4 5 6
2 2 11 7 6 11


Output

37.7044021497

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
const double EPS = 10e-11;
class VagueDouble {
 public:
  double vd;
  VagueDouble() { vd = nan(""); }
  VagueDouble(const double d) { vd = d; }
  VagueDouble operator+(const VagueDouble VD) const {
    return VagueDouble(vd + VD.vd);
  }
  VagueDouble operator-(const VagueDouble VD) const {
    return VagueDouble(vd - VD.vd);
  }
  VagueDouble operator*(const VagueDouble VD) const {
    return VagueDouble(vd * VD.vd);
  }
  VagueDouble operator/(const VagueDouble VD) const {
    return VagueDouble(vd / VD.vd);
  }
  VagueDouble operator+(const double d) const { return VagueDouble(vd + d); }
  VagueDouble operator-(const double d) const { return VagueDouble(vd - d); }
  VagueDouble operator*(const double d) const { return VagueDouble(vd * d); }
  VagueDouble operator/(const double d) const { return VagueDouble(vd / d); }
  bool operator<(const VagueDouble VD) const {
    return vd + EPS < VD.vd && vd + EPS * abs(vd) < VD.vd;
  }
  bool operator>(const VagueDouble VD) const {
    return vd - EPS > VD.vd && vd - EPS * abs(vd) > VD.vd;
  }
  bool operator==(const VagueDouble VD) const {
    return !(*this < VD.vd) && !(*this > VD.vd);
  }
  bool operator<(const double d) const { return *this < VagueDouble(d); }
  bool operator>(const double d) const { return *this > VagueDouble(d); }
  bool operator==(const double d) const { return *this == VagueDouble(d); }
  void operator+=(const VagueDouble VD) { *this = *this + VD; }
  void operator-=(const VagueDouble VD) { *this = *this - VD; }
  void operator*=(const VagueDouble VD) { *this = *this * VD; }
  void operator/=(const VagueDouble VD) { *this = *this / VD; }
  friend VagueDouble operator+(const double d, const VagueDouble &VD) {
    return VagueDouble(d) + VD;
  }
  friend VagueDouble operator-(const double d, const VagueDouble &VD) {
    return VagueDouble(d) - VD;
  }
  friend VagueDouble operator*(const double d, const VagueDouble &VD) {
    return VagueDouble(d) * VD;
  }
  friend VagueDouble operator/(const double d, const VagueDouble &VD) {
    return VagueDouble(d) / VD;
  }
  friend bool operator<(const double d, const VagueDouble &VD) {
    return VagueDouble(d) < VD;
  }
  friend bool operator>(const double d, const VagueDouble &VD) {
    return VagueDouble(d) > VD;
  }
  friend bool operator==(const double d, const VagueDouble &VD) {
    return VagueDouble(d) == VD;
  }
  double to_double() { return vd; }
  friend std::ostream &operator<<(std::ostream &os, const VagueDouble VD) {
    os << VD.vd;
    return os;
  }
  friend std::istream &operator>>(std::istream &is, VagueDouble &VD) {
    double d;
    is >> d;
    VD = VagueDouble(d);
    return is;
  }
};
VagueDouble abs(VagueDouble VD) { return (VD.vd < 0) ? (-VD.vd) : VD.vd; }
VagueDouble sqr(VagueDouble VD) { return VD.vd * VD.vd; }
VagueDouble sqr(double d) { return d * d; }
VagueDouble sqrt(VagueDouble VD) { return VagueDouble(sqrt(VD.vd)); }
bool isnan(VagueDouble VD) { return isnan(VD.vd); }
class P {
 private:
 public:
  VagueDouble x, y;
  P() {
    x = nan("");
    y = nan("");
  }
  P(double _x, double _y) {
    x = _x;
    y = _y;
  }
  P(VagueDouble _x, VagueDouble _y) {
    x = _x;
    y = _y;
  }
  P operator+(const P p) const { return P(x + p.x, y + p.y); }
  P operator-(const P p) const { return P(x - p.x, y - p.y); }
  P operator*(const double d) const { return P(x * d, y * d); }
  P operator/(const double d) const { return P(x / d, y / d); }
  bool operator<(const P &p) const {
    return (x == p.x) ? (y < p.y) : (x < p.x);
  }
  bool operator>(const P &p) const {
    return (x == p.x) ? (y > p.y) : (x > p.x);
  }
  bool operator==(const P &p) const { return (x == p.x) && (y == p.y); }
  void operator+=(const P &p) { *this = *this + p; }
  void operator-=(const P &p) { *this = *this - p; }
  void operator*=(const double &p) { *this = *this * p; }
  void operator/=(const double &p) { *this = *this / p; }
  friend std::ostream &operator<<(std::ostream &os, const P &p) {
    os << p.x.vd << " " << p.y.vd;
    return os;
  }
  friend std::istream &operator>>(std::istream &is, P &p) {
    double _x, _y;
    is >> _x >> _y;
    p = P(_x, _y);
    return is;
  }
};
VagueDouble dist(P p0, P p1) {
  return sqrt(sqr(p0.x - p1.x) + sqr(p0.y - p1.y));
}
VagueDouble area(P p0, P p1, P p2) {
  return abs((p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y)) /
         0.5;
}
VagueDouble distPL(P l0, P l1, P p) {
  if (l0 == l1) return dist(l0, p);
  VagueDouble dx = l0.x - l1.x;
  VagueDouble dy = l0.y - l1.y;
  return abs(dy * (l0.x - p.x) - dx * (l0.y - p.y)) / sqrt(dx * dx + dy * dy);
}
bool isnan(P p) { return isnan(p.x); }
bool onLine(P l0, P l1, P p) {
  if (l0 == l1) return l0 == p;
  if (p.x < min(l0.x, l1.x) || max(l0.x, l1.x) < p.x) return false;
  if (p.y < min(l0.y, l1.y) || max(l0.y, l1.y) < p.y) return false;
  return distPL(l0, l1, p) == 0;
}
P findCross(P a0, P a1, P b0, P b1) {
  P a = a0 - a1, b = b0 - b1, res;
  if (abs(a.x * b.y - a.y * b.x) == 0) return res;
  res.x = (a.x * b.x * (a0.y - b0.y) + a.x * b.y * b0.x - a.y * b.x * a0.x) /
          (a.x * b.y - a.y * b.x);
  res.y = (a.y * b.y * (a0.x - b0.x) + a.y * b.x * b0.y - a.x * b.y * a0.y) /
          (a.y * b.x - a.x * b.y);
  if (res.x < min(a0.x, a1.x) || max(a0.x, a1.x) < res.x) return P();
  if (res.x < min(b0.x, b1.x) || max(b0.x, b1.x) < res.x) return P();
  if (res.y < min(a0.y, a1.y) || max(a0.y, a1.y) < res.y) return P();
  if (res.y < min(b0.y, b1.y) || max(b0.y, b1.y) < res.y) return P();
  return res;
}
class Polygon {
 private:
 public:
  vector<P> points;
  Polygon() {}
  Polygon(vector<P> vec) { points = vec; }
  Polygon(int num) { points.resize(num); }
  int size() { return ((int)(points).size()); }
  P &operator[](int pos) { return points[pos]; }
  bool onPoly(P p) {
    int n = ((int)(points).size());
    for (int i = 0; i < ((int)(n)); ++i)
      if (onLine(points[i], points[(i + 1) % n], p)) return true;
    return false;
  }
  bool inPoly(P p) {
    int n = ((int)(points).size());
    if (n == 0) return false;
    if (onPoly(p)) return true;
    P right_point = p;
    for (int i = 0; i < ((int)(n)); ++i)
      right_point.x = max(right_point.x, points[i].x);
    if (right_point == p) return false;
    int cnt = 0;
    for (int i = 0; i < ((int)(n)); ++i) {
      P cross = findCross(points[i], points[(i + 1) % n], p, right_point);
      if (!isnan(cross)) cnt++;
    }
    for (int i = 0; i < ((int)(((int)(points).size()))); ++i)
      if (onLine(p, right_point, points[i])) {
        VagueDouble dy0 = points[(i - 1 + n) % n].y - p.y;
        VagueDouble dy1 = points[(i + 1 + n) % n].y - p.y;
        if (dy0 * dy1 < 0) cnt++;
      }
    return cnt % 2 == 1;
  }
  friend std::ostream &operator<<(std::ostream &os, Polygon &poly) {
    for (int i = 0; i < ((int)(((int)(poly).size()))); ++i)
      os << poly[i] << " ";
    return os;
  }
  friend std::istream &operator>>(std::istream &is, Polygon &poly) {
    for (int i = 0; i < ((int)(((int)(poly).size()))); ++i) is >> poly[i];
    return is;
  }
};
int main() {
  int n;
  cin >> n;
  vector<Polygon> base(n, Polygon(3));
  for (int i = 0; i < ((int)(n)); ++i) cin >> base[i];
  set<P> seg[10005];
  for (int i = 0; i < ((int)(((int)(base).size()))); ++i)
    for (int j = 0; j < ((int)(((int)(base[i]).size()))); ++j)
      seg[i * 3 + j].insert(base[i][(j + 0) % 3]);
  for (int i = 0; i < ((int)(((int)(base).size()))); ++i)
    for (int j = 0; j < ((int)(((int)(base[i]).size()))); ++j)
      seg[i * 3 + j].insert(base[i][(j + 1) % 3]);
  for (int i = 0; i < ((int)(((int)(base).size()))); ++i)
    for (int j = 0; j < ((int)(((int)(base[i]).size()))); ++j)
      for (int k = 0; k < ((int)(((int)(base).size()))); ++k)
        for (int l = 0; l < ((int)(((int)(base[k]).size()))); ++l) {
          if (i == k) continue;
          P cross = findCross(base[i][j], base[i][(j + 1) % 3], base[k][l],
                              base[k][(l + 1) % 3]);
          if (isnan(cross)) continue;
          seg[i * 3 + j].insert(cross);
        }
  VagueDouble res = 0.0;
  vector<P> vec[10005];
  for (int i = 0; i < ((int)(((int)(base).size()))); ++i)
    for (int j = 0; j < ((int)(((int)(base[i]).size()))); ++j)
      for (__typeof((seg[i * 3 + j]).begin()) it = (seg[i * 3 + j]).begin();
           it != (seg[i * 3 + j]).end(); it++)
        vec[i * 3 + j].push_back(*it);
  for (int i = 0; i < ((int)(((int)(base).size()))); ++i)
    for (int j = 0; j < ((int)(((int)(base[i]).size()))); ++j)
      for (int k = 0; k < ((int)(((int)(vec[i * 3 + j]).size()) - 1)); ++k) {
        P mid = (vec[i * 3 + j][k] + vec[i * 3 + j][k + 1]) / 2.0;
        bool ok = true;
        for (int l = 0; l < ((int)(((int)(base).size()))); ++l)
          if (i != l && base[l].inPoly(mid)) {
            ok = false;
            break;
          }
        if (ok) res += dist(vec[i * 3 + j][k], vec[i * 3 + j][k + 1]);
      }
  printf("%0.20lf\n", res.to_double());
}