#include <bits/stdc++.h>
using namespace std;
double fgcd(double a, double b) { return a < 0.0001 ? b : fgcd(fmod(b, a), a); }
int main() {
  double a, b, c;
  double x1, x2, x3, y1, y2, y3;
  double k, r;
  cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
  a = sqrt((x1 - x2) * (x1 - x2) + (y2 - y1) * (y2 - y1));
  b = sqrt((x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3));
  c = sqrt((x3 - x2) * (x3 - x2) + (y3 - y2) * (y3 - y2));
  k = (a + b + c) / 2.0;
  r = (a * b * c) / (4 * sqrt(k * (k - a) * (k - b) * (k - c)));
  double temp;
  if (a > c) {
    temp = a;
    a = c;
    c = temp;
  }
  if (b > c) {
    temp = b;
    b = c;
    c = temp;
  }
  double aa, bb, cc;
  aa = 2 * asin(a / (2 * r));
  bb = 2 * asin(b / (2 * r));
  cc = 2 * 3.14159265358979323846 - aa - bb;
  double mdzz;
  mdzz = fgcd(aa, bb);
  mdzz = fgcd(mdzz, cc);
  printf("%.6lf\n", (r * r * sin(mdzz) * 3.14159265358979323846) / mdzz);
  return 0;
}
