#include <bits/stdc++.h>
using namespace std;
double PI = 3.141592654;
double fgcd(double a, double b) {
  if (fabs(a) < 0.01) return b;
  if (fabs(b) < 0.01) return a;
  return fgcd(b, fmod(a, b));
}
int main() {
  cin.sync_with_stdio(false);
  double x1, x2, x3, y1, y2, y3;
  cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
  double ab, bc, ac;
  ab = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  ac = sqrt((x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3));
  bc = sqrt((x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3));
  double p = (ab + bc + ac) / 2.0;
  double S = sqrt(p * (p - ab) * (p - ac) * (p - bc));
  double r = ab * bc * ac / (4.0 * S);
  double co1, co2, co3;
  if (ab < ac) swap(ab, ac);
  if (ab < bc) swap(ab, bc);
  co1 = (2.0 * r * r - ac * ac) / (2 * r * r);
  co2 = (2.0 * r * r - bc * bc) / (2 * r * r);
  co3 = (2.0 * r * r - ab * ab) / (2 * r * r);
  double j1, j2, j3;
  j1 = acos(co1);
  j2 = acos(co2);
  j3 = 2.0 * PI - j1 - j2;
  double q = fgcd(j1, fgcd(j2, j3));
  double S2;
  printf("%0.8lf", r * r * sin(q) * PI / q);
  return 0;
}
