#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
double diameter(double a, double b, double c);
double fgcd(double a, double b);
int main() {
  double x[3], y[3];
  double edge[3];
  for (int i = 0; i < 3; ++i) {
    scanf("%lf%lf", &x[i], &y[i]);
  }
  for (int i = 0; i < 3; ++i) {
    edge[i] = sqrt((x[i] - x[(i + 1) % 3]) * (x[i] - x[(i + 1) % 3]) +
                   (y[i] - y[(i + 1) % 3]) * (y[i] - y[(i + 1) % 3]));
  }
  double r = diameter(edge[0], edge[1], edge[2]);
  double angle[3];
  for (int i = 0; i < 2; ++i) {
    angle[i] = acos(1 - edge[i] * edge[i] / (2 * r * r));
  }
  angle[2] = 2 * pi - angle[0] - angle[1];
  double angle_fgcd = fgcd(angle[0], fgcd(angle[1], angle[2]));
  double s = pi / angle_fgcd * r * r * sin(angle_fgcd);
  printf("%.6f\n", s);
  return 0;
}
double diameter(double a, double b, double c) {
  double p = (a + b + c) / 2;
  double s = sqrt(p * (p - a) * (p - b) * (p - c));
  return a * b * c / (4 * s);
}
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));
}
