#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1.0);
const double eps = 1e-4;
double gcd(double x, double y) {
  while (fabs(x) > eps && fabs(y) > eps) {
    if (x > y)
      x -= floor(x / y) * y;
    else
      y -= floor(y / x) * x;
  }
  return x + y;
}
double a_cos(double a, double b, double c) {
  return acos((a * a + b * b - c * c) / (2 * a * b));
}
int main() {
  double x1, y1, x2, y2, x3, y3;
  cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
  double a = sqrt((x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3));
  double b = sqrt((x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3));
  double c = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  double A = a_cos(b, c, a);
  double B = a_cos(a, c, b);
  double C = a_cos(a, b, c);
  double P = (a + b + c) / 2;
  double S = sqrt(P * (P - a) * (P - b) * (P - c));
  double R = (a * b * c) / (4 * S);
  double N = PI / gcd(A, gcd(B, C));
  cout.precision(10);
  cout << fixed;
  cout << 0.5 * R * R * sin(2 * PI / N) * N;
  return 0;
}
