#include <bits/stdc++.h>
using namespace std;
double getLength(double x1, double y1, double x2, double y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
double getR(double a, double b, double c) {
  double p = (a + b + c) / 2.0;
  return (a * b * c) / 4 / sqrt(p * (p - a) * (p - b) * (p - c));
}
double getAngle(double a, double r) {
  return acos((2 * r * r - a * a) / 2 / r / r);
}
double gcd(double a, double b) {
  if (a < 1e-3) return b;
  if (b < 1e-3) return a;
  return gcd(b, fmod(a, b));
}
int main() {
  ios_base::sync_with_stdio(false);
  double x1, y1, x2, y2, x3, y3;
  cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
  double pi = 3.1415926589;
  double a = getLength(x2, y2, x3, y3);
  double b = getLength(x3, y3, x1, y1);
  double c = getLength(x1, y1, x2, y2);
  double R = getR(a, b, c);
  double A = getAngle(a, R);
  double B = getAngle(b, R);
  double C = 2 * pi - A - B;
  double g = gcd(gcd(A, B), C);
  double x = pi / g;
  double res = sin(g) * (pi / g) * R * R;
  printf("%.8f\n", res);
  return 0;
}
