#include <bits/stdc++.h>
using namespace std;
using namespace std;
const double PI = acos(-1);
struct Point {
  double x;
  double y;
};
void swap(double &a, double &b) {
  double t;
  t = a;
  a = b;
  b = t;
}
bool find_center(Point *p, Point &c) {
  double dx1 = p[1].x - p[0].x;
  double dy1 = p[1].y - p[0].y;
  double dx2 = p[2].x - p[0].x;
  double dy2 = p[2].y - p[0].y;
  if ((fabs((dx1 * dx2 + dy1 * dy2) - (0)) < 1E-2)) {
    c.x = (p[1].x + p[2].x) / 2;
    c.y = (p[1].y + p[2].y) / 2;
    return true;
  }
  if ((fabs((dx1 * dy2) - (dx2 * dy1)) < 1E-2)) return false;
  double mx1 = (p[1].x + p[0].x) / 2;
  double my1 = (p[1].y + p[0].y) / 2;
  double mx2 = (p[2].x + p[0].x) / 2;
  double my2 = (p[2].y + p[0].y) / 2;
  double a1 = dx1, b1 = dy1, c1 = -mx1 * dx1 - my1 * dy1;
  double a2 = dx2, b2 = dy2, c2 = -mx2 * dx2 - my2 * dy2;
  c.x = (c1 * b2 - c2 * b1) / (a2 * b1 - a1 * b2);
  c.y = (c1 * a2 - c2 * a1) / (a1 * b2 - a2 * b1);
  return true;
}
double fgcd(double a, double b) {
  if ((fabs((a) - (0)) < 1E-2)) return b;
  if ((fabs((b) - (0)) < 1E-2)) return a;
  return fgcd(b, fmod(a, b));
}
int main() {
  Point tri[4];
  while (1) {
    for (int i = 1; i <= 3; i++) {
      if (!~scanf("%lf%lf", &tri[i].x, &tri[i].y)) return 0;
    }
    find_center(&tri[1], tri[0]);
    double r = sqrt((tri[1].x - tri[0].x) * (tri[1].x - tri[0].x) +
                    (tri[1].y - tri[0].y) * (tri[1].y - tri[0].y));
    double l1 = sqrt((tri[2].x - tri[3].x) * (tri[2].x - tri[3].x) +
                     (tri[2].y - tri[3].y) * (tri[2].y - tri[3].y));
    double l2 = sqrt((tri[1].x - tri[3].x) * (tri[1].x - tri[3].x) +
                     (tri[1].y - tri[3].y) * (tri[1].y - tri[3].y));
    double l3 = sqrt((tri[1].x - tri[2].x) * (tri[1].x - tri[2].x) +
                     (tri[1].y - tri[2].y) * (tri[1].y - tri[2].y));
    if (l3 < l1) {
      swap(l1, l3);
    }
    if (l3 < l2) {
      swap(l2, l3);
    }
    double angle1 = acos(1 - (l1 / r) * (l1 / r) / 2) * 180 / PI;
    double angle2 = acos(1 - (l2 / r) * (l2 / r) / 2) * 180 / PI;
    double angle3 = 360 - angle1 - angle2;
    double e = 360 / fgcd(angle1, fgcd(angle2, angle3));
    double angle = 360 / e;
    printf("%.8f\n", sin(angle * PI / 180) * r * r * e / 2);
  }
}
