#include <bits/stdc++.h>
const double EPS = 1e-4;
const double PI = acos(-1);
double fgcd(double a, double b) {
  return fabs(b) < EPS ? fabs(a) : fgcd(b, fmod(a, b));
}
int main() {
  using namespace std;
  ios_base::sync_with_stdio(false), cin.tie(nullptr);
  cout.precision(7), cout << fixed;
  vector<pair<double, double> > P(3);
  for (auto &p : P) cin >> p.first >> p.second;
  double a, b, c;
  a = hypot(P[1].first - P[0].first, P[1].second - P[0].second);
  b = hypot(P[2].first - P[0].first, P[2].second - P[0].second);
  c = hypot(P[2].first - P[1].first, P[2].second - P[1].second);
  double p = (a + b + c) / 2;
  double S = sqrt(p * (p - a) * (p - b) * (p - c));
  double r = (a * b * c) / (4 * S);
  double A, B, C;
  A = acos(1 - (a * a) / (2 * r * r));
  B = acos(1 - (b * b) / (2 * r * r));
  C = 2 * PI - A - B;
  double angle = fgcd(A, fgcd(B, C));
  double side = sqrt(2 * r * r * (1 - cos(angle)));
  double s = (r * 2 + side) / 2;
  cout << sqrt(s * (s - r) * (s - r) * (s - side)) * ((2 * PI) / angle);
}
