#include <bits/stdc++.h>
using namespace std;
double x[4], y[4], eps = 1e-4, pi = acos(-1);
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;
}
int main() {
  for (int i = 1; i <= 3; i++) scanf("%lf%lf", x + i, y + i);
  double a = sqrt(pow((x[1] - x[2]), 2) + pow(y[1] - y[2], 2));
  double b = sqrt(pow((x[2] - x[3]), 2) + pow(y[2] - y[3], 2));
  double c = sqrt(pow((x[1] - x[3]), 2) + pow(y[1] - y[3], 2));
  double cosA = (b * b + c * c - a * a) / (2 * b * c);
  double sinA = sqrt(1 - cosA * cosA);
  double r = a / 2 / sinA;
  double A = acos(cosA);
  double B = acos((a * a - b * b + c * c) / (2 * a * c));
  double C = acos((a * a + b * b - c * c) / (2 * a * b));
  double n = pi / gcd(gcd(A, B), C);
  printf("%.8lf", n / 2 * r * r * sin(2 * pi / n));
  return 0;
}
