#include <bits/stdc++.h>
using namespace std;
double dis(double x1, double y1, double x2, double y2) {
  double d = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
  return sqrt(d);
}
double getcos(double a, double r) {
  double cos1 = (r * r + r * r - a * a) / (2 * r * r);
  return cos1;
}
double gcd(double a, double b) {
  if (fabs(b) < 1e-2) return a;
  return gcd(b, fmod(a, b));
}
int main() {
  double x1, y1, x2, y2, x3, y3;
  cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
  double d1, d2, d3;
  d1 = dis(x1, y1, x2, y2);
  d2 = dis(x1, y1, x3, y3);
  d3 = dis(x2, y2, x3, y3);
  double p = (d1 + d2 + d3) / 2.0;
  double s = sqrt(p * (p - d1) * (p - d2) * (p - d3));
  double R = d1 * d2 * d3 / s / 4.0;
  double angle1 = acos(getcos(d1, R));
  double angle2 = acos(getcos(d2, R));
  double angle3 = 2 * acos(-1.0) - angle1 - angle2;
  double angle = gcd(angle3, gcd(angle1, angle2));
  printf("%.6f", acos(-1.0) * R * R * sin(angle) / angle);
  return 0;
}
