#include <bits/stdc++.h>
using namespace std;
int main() {
  double x[6], y[6], al[3], lm, r, s, a[3], eps = 1e-4, ans, pi = acos(-1.),
                                            tmp, tmp1, tmp2;
  int i, j, f;
  for (i = 0; i < 3; i++) {
    scanf("%lf %lf", &x[i], &y[i]);
    x[i + 3] = x[i];
    y[i + 3] = y[i];
  }
  for (i = 0; i < 3; i++)
    al[i] = 2. * acos(((x[i + 1] - x[i]) * (x[i + 2] - x[i]) +
                       (y[i + 1] - y[i]) * (y[i + 2] - y[i])) /
                      sqrt(((x[i + 1] - x[i]) * (x[i + 1] - x[i]) +
                            (y[i + 1] - y[i]) * (y[i + 1] - y[i])) *
                           ((x[i + 2] - x[i]) * (x[i + 2] - x[i]) +
                            (y[i + 2] - y[i]) * (y[i + 2] - y[i]))));
  for (i = 3; i <= 100; i++) {
    for (j = f = 0; j < 3; j++) {
      tmp1 = al[j] * i;
      tmp2 = al[j] * i / (2. * pi);
      tmp = tmp1 - (int)(tmp2)*2. * pi;
      if (fabs(2. * pi - tmp) < eps) tmp -= 2. * pi;
      if (fabs(2. * pi + tmp) < eps) tmp += 2. * pi;
      if (tmp > eps) {
        f = 1;
        break;
      }
    }
    if (!f) {
      for (j = 0; j < 3; j++)
        a[j] = sqrt((x[j + 1] - x[j]) * (x[j + 1] - x[j]) +
                    (y[j + 1] - y[j]) * (y[j + 1] - y[j]));
      s = fabs((x[1] - x[0]) * (y[2] - y[0]) - (x[2] - x[0]) * (y[1] - y[0]));
      r = a[0] * a[1] * a[2] / (2. * s);
      lm = 2. * pi / i;
      ans = i * r * r * sin(lm) / 2.;
      printf("%.10lf\n", ans);
      return 0;
    }
  }
}
