#include <bits/stdc++.h>
using namespace std;
double eps = 1e-5;
double sq(double x[], double y[]) {
  return 0.5 *
         fabs((x[2] - x[0]) * (y[1] - y[0]) - (x[1] - x[0]) * (y[2] - y[0]));
}
double len(double x[], double y[], int i, int j) {
  return (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]);
}
double sq(double x) { return x * x; }
int main() {
  double x[3], y[3];
  for (int i = 0; i < 3; i++) {
    cin >> x[i] >> y[i];
  }
  double r_2 = (len(x, y, 0, 1) * len(x, y, 0, 2) * len(x, y, 1, 2)) /
               sq(4.0 * sq(x, y));
  double a[3];
  for (int i = 0; i < 3; i++) {
    a[i] = acos(1.0 - len(x, y, i, (i + 1) % 3) / (2.0 * r_2));
  }
  for (int i = 3; i <= 100; i++) {
    double x = (4 * acos(0.0)) / i;
    bool is = 1;
    for (int j = 0; j < 3; j++) {
      if (fabs(sin(a[j] * i * 0.5)) >= eps) {
        is = 0;
      }
    }
    if (is) {
      printf("%0.7lf", i * (0.5 * r_2 * sin(x)));
      return 0;
    }
  }
}
