#include <bits/stdc++.h>
using namespace std;
const double PI = 3.141592653589793238463;
double gcd(double x, double y) {
  double eps = 1e-4;
  while (fabs(x) > eps && fabs(y) > eps) {
    if (x > y)
      x -= floor(x / y) * y;
    else
      y -= floor(y / x) * x;
  }
  return (x + y);
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  double ar, aa, bb, cc, n, r, s, a, b, c, x1, y1, x2, y2, x3, y3;
  cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
  a = sqrt((x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3));
  b = sqrt((x3 - x1) * (x3 - x1) + (y3 - y1) * (y3 - y1));
  c = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
  s = (a + b + c) / 2.0;
  ar = sqrt(s * (s - a) * (s - b) * (s - c));
  r = a * b * c / 4.0 / ar;
  aa = acos((b * b + c * c - a * a) / 2.0 / b / c);
  bb = acos((c * c + a * a - b * b) / 2.0 / c / a);
  cc = acos((a * a + b * b - c * c) / 2.0 / a / b);
  n = PI / gcd(aa, gcd(bb, cc));
  ar = n * r * r / 2.0 * sin(2.0 * PI / n);
  cout << fixed << setprecision(8) << ar << '\n';
  return 0;
}
