#include <bits/stdc++.h>
using namespace std;
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() {
  double x[3], y[3], z[3], angle[3];
  for (int i = 0; i < 3; i++) cin >> x[i] >> y[i];
  for (int i = 0; i < 3; i++)
    z[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 q = (z[0] + z[1] + z[2]) / 2;
  double S = sqrt(q * (q - z[0]) * (q - z[1]) * (q - z[2]));
  double r = (z[0] * z[1] * z[2]) / (4 * S);
  for (int i = 0; i < 2; i++) angle[i] = acos(1 - z[i] * z[i] / (2 * r * r));
  angle[2] = 2 * acos(-1.0) - angle[0] - angle[1];
  double min = fgcd(angle[0], fgcd(angle[1], angle[2]));
  printf("%.6lf\n", r * r * sin(min) / 2 * (2 * acos(-1.0) / min));
}
