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;
double PI = acos(-1);
class VagueDouble {
 public:
  double vd;
  VagueDouble() { vd = nan(""); }
  VagueDouble(const double d) { vd = d; }
  inline VagueDouble operator-() const { return VagueDouble(-vd); }
  inline VagueDouble operator+(const VagueDouble VD) const {
    return VagueDouble(vd + VD.vd);
  }
  inline VagueDouble operator-(const VagueDouble VD) const {
    return VagueDouble(vd - VD.vd);
  }
  inline VagueDouble operator*(const VagueDouble VD) const {
    return VagueDouble(vd * VD.vd);
  }
  inline VagueDouble operator/(const VagueDouble VD) const {
    return VagueDouble(vd / VD.vd);
  }
  inline VagueDouble operator+(const double d) const {
    return VagueDouble(vd + d);
  }
  inline VagueDouble operator-(const double d) const {
    return VagueDouble(vd - d);
  }
  inline VagueDouble operator*(const double d) const {
    return VagueDouble(vd * d);
  }
  inline VagueDouble operator/(const double d) const {
    return VagueDouble(vd / d);
  }
  inline bool operator<(const VagueDouble VD) const {
    return vd + EPS < VD.vd && vd + EPS * abs(vd) < VD.vd;
  }
  inline bool operator>(const VagueDouble VD) const {
    return vd - EPS > VD.vd && vd - EPS * abs(vd) > VD.vd;
  }
  inline bool operator==(const VagueDouble VD) const {
    return !(*this < VD.vd) && !(*this > VD.vd);
  }
  inline bool operator<=(const VagueDouble VD) const {
    return !(*this > VD.vd);
  }
  inline bool operator>=(const VagueDouble VD) const {
    return !(*this < VD.vd);
  }
  inline bool operator<(const double d) const { return *this < VagueDouble(d); }
  inline bool operator>(const double d) const { return *this > VagueDouble(d); }
  inline bool operator==(const double d) const {
    return *this == VagueDouble(d);
  }
  inline bool operator<=(const double d) const {
    return *this <= VagueDouble(d);
  }
  inline bool operator>=(const double d) const {
    return *this >= VagueDouble(d);
  }
  inline void operator+=(const VagueDouble VD) { *this = *this + VD; }
  inline void operator-=(const VagueDouble VD) { *this = *this - VD; }
  inline void operator*=(const VagueDouble VD) { *this = *this * VD; }
  inline void operator/=(const VagueDouble VD) { *this = *this / VD; }
  inline friend VagueDouble operator+(const double d, const VagueDouble &VD) {
    return VagueDouble(d) + VD;
  }
  inline friend VagueDouble operator-(const double d, const VagueDouble &VD) {
    return VagueDouble(d) - VD;
  }
  inline friend VagueDouble operator*(const double d, const VagueDouble &VD) {
    return VagueDouble(d) * VD;
  }
  inline friend VagueDouble operator/(const double d, const VagueDouble &VD) {
    return VagueDouble(d) / VD;
  }
  inline friend bool operator<(const double d, const VagueDouble &VD) {
    return VagueDouble(d) < VD;
  }
  inline friend bool operator>(const double d, const VagueDouble &VD) {
    return VagueDouble(d) > VD;
  }
  inline friend bool operator==(const double d, const VagueDouble &VD) {
    return VagueDouble(d) == VD;
  }
  inline friend bool operator<=(const double d, const VagueDouble &VD) {
    return VagueDouble(d) <= VD;
  }
  inline friend bool operator>=(const double d, const VagueDouble &VD) {
    return VagueDouble(d) >= VD;
  }
  inline friend std::ostream &operator<<(std::ostream &os,
                                         const VagueDouble VD) {
    os << VD.vd;
    return os;
  }
  inline friend std::istream &operator>>(std::istream &is, VagueDouble &VD) {
    double d;
    is >> d;
    VD = VagueDouble(d);
    return is;
  }
  inline double to_double() { return vd; }
};
inline VagueDouble abs(VagueDouble VD) {
  return (VD.vd < 0) ? (-VD.vd) : VD.vd;
}
inline VagueDouble sqr(VagueDouble VD) { return VD.vd * VD.vd; }
inline VagueDouble sqr(double d) { return d * d; }
inline VagueDouble sqrt(VagueDouble VD) { return VagueDouble(sqrt(VD.vd)); }
inline bool isnan(VagueDouble VD) { return isnan(VD.vd); }
class P {
 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 { return P(-x, -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 length() { return sqrt(x * x + y * y); }
  VagueDouble operator*(const P p) const { return x * p.x + y * p.y; }
  VagueDouble operator^(const P p) const { return x * p.y - y * p.x; }
};
inline VagueDouble dist(P p0, P p1) {
  return sqrt(sqr(p0.x - p1.x) + sqr(p0.y - p1.y));
}
inline VagueDouble area(P p0, P p1, P p2) {
  return abs((p1 - p0) ^ (p2 - p0)) * 0.5;
}
inline bool isnan(P p) { return isnan(p.x); }
VagueDouble distPL(P l0, P l1, P p) {
  if (l0 == l1) return dist(l0, p);
  return abs((p - l0) ^ (l1 - l0)) / (l1 - l0).length();
}
VagueDouble angle(P from0, P to0, P from1, P to1) {
  P v0 = to0 - from0;
  P v1 = to1 - from1;
  VagueDouble res = atan2(v1.y.vd, v1.x.vd) - atan2(v0.y.vd, v0.x.vd);
  while (res < 0) res += PI * 2.0;
  return res;
}
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;
  VagueDouble den = a ^ b;
  if (den == 0) return P();
  res.x =
      (a.x * b.x * (a0.y - b0.y) + a.x * b.y * b0.x - a.y * b.x * a0.x) / den;
  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();
  res.y =
      -(a.y * b.y * (a0.x - b0.x) + a.y * b.x * b0.y - a.x * b.y * a0.y) / den;
  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 {
 public:
  vector<P> points;
  Polygon() {}
  Polygon(vector<P> vec) { points = vec; }
  Polygon(long long int num) { points.resize(num); }
  friend std::ostream &operator<<(std::ostream &os, Polygon &poly) {
    for (long long int i = 0;
         i < ((long long int)(((long long int)(poly).size()))); ++i)
      os << poly[i] << " ";
    return os;
  }
  friend std::istream &operator>>(std::istream &is, Polygon &poly) {
    for (long long int i = 0;
         i < ((long long int)(((long long int)(poly).size()))); ++i)
      is >> poly[i];
    return is;
  }
  long long int size() { return ((long long int)(points).size()); }
  P &operator[](long long int pos) { return points[pos]; }
  bool onPoly(P p) {
    long long int n = ((long long int)(points).size());
    if (onLine(points[n - 1], points[0], p)) return true;
    for (long long int i = 0; i < ((long long int)(n - 1)); ++i)
      if (onLine(points[i], points[i + 1], p)) return true;
    return false;
  }
  bool inPoly(P p) {
    long long int n = ((long long int)(points).size());
    if (n == 0) return false;
    if (onPoly(p)) return true;
    P right_point = p;
    for (long long int i = 0; i < ((long long int)(n)); ++i)
      right_point.x = max(right_point.x, points[i].x);
    if (right_point == p) return false;
    long long int cnt = 0;
    for (long long int i = 0, next = 1; i < n; i++, next++) {
      if (next == n) next = 0;
      if (0 < (points[i].y - p.y) * (points[next].y - p.y)) continue;
      P cross = findCross(points[i], points[next], p, right_point);
      if (!isnan(cross)) cnt++;
    }
    for (long long int i = 0;
         i < ((long long int)(((long long 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 & 1);
  }
  void convexReform() {
    long long int k = 0;
    if (((long long int)(points).size()) <= 1) return;
    sort(points.begin(), points.end());
    vector<P> ans(2 * ((long long int)(points).size()));
    for (long long int i = 0; i < ((long long int)(points).size());
         ans[k++] = points[i++]) {
      while (2 <= k &&
             0 <= ((ans[k - 1] - ans[k - 2]) ^ (points[i] - ans[k - 2])))
        k--;
    }
    for (long long int i = ((long long int)(points).size()) - 2, t = k + 1;
         0 <= i; ans[k++] = points[i--]) {
      while (t <= k &&
             0 <= ((ans[k - 1] - ans[k - 2]) ^ (points[i] - ans[k - 2])))
        k--;
    }
    ans.resize(k - 1);
    points = ans;
  }
};
int main() {
  long long int n;
  cin >> n;
  vector<Polygon> base(n, Polygon(3));
  for (long long int i = 0; i < ((long long int)(n)); ++i) cin >> base[i];
  set<P> seg[10005];
  for (long long int i = 0;
       i < ((long long int)(((long long int)(base).size()))); ++i)
    for (long long int j = 0;
         j < ((long long int)(((long long int)(base[i]).size()))); ++j)
      seg[i * 3 + j].insert(base[i][(j + 0) % 3]);
  for (long long int i = 0;
       i < ((long long int)(((long long int)(base).size()))); ++i)
    for (long long int j = 0;
         j < ((long long int)(((long long int)(base[i]).size()))); ++j)
      seg[i * 3 + j].insert(base[i][(j + 1) % 3]);
  for (long long int i = 0;
       i < ((long long int)(((long long int)(base).size()))); ++i)
    for (long long int j = 0;
         j < ((long long int)(((long long int)(base[i]).size()))); ++j)
      for (long long int k = 0; k < ((long long int)(i)); ++k)
        for (long long int l = 0;
             l < ((long long int)(((long long 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);
          seg[k * 3 + l].insert(cross);
        }
  VagueDouble res = 0.0;
  vector<P> vec[10005];
  for (long long int i = 0;
       i < ((long long int)(((long long int)(base).size()))); ++i)
    for (long long int j = 0;
         j < ((long long int)(((long long 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 (long long int i = 0;
       i < ((long long int)(((long long int)(base).size()))); ++i)
    for (long long int j = 0;
         j < ((long long int)(((long long int)(base[i]).size()))); ++j)
      for (long long int k = 0;
           k < ((long long int)(((long long 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 (long long int l = 0;
             l < ((long long int)(((long long 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());
}