#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 10;
const double eps = 1e-3, pi = acos(-1);
inline long long rd() {
  long long x = 0, w = 1;
  char ch = 0;
  while (ch < '0' || ch > '9') {
    if (ch == '-') w = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    x = (x << 3) + (x << 1) + (ch ^ 48);
    ch = getchar();
  }
  return x * w;
}
double a[3][2], l[4], ag[3], r, d, n;
inline double sq(double x) { return x * x; }
inline double dis(int i, int j) {
  return sqrt(sq(a[i][0] - a[j][0]) + sq(a[i][1] - a[j][1]));
}
inline double S(double a, double b, double c) {
  double p = (a + b + c) / 2;
  return sqrt(p * (p - a) * (p - b) * (p - c));
}
inline double gcd(double a, double b, double c) {
  for (double i = 1;; ++i) {
    double an = a / i, aa = a / an - floor(a / an), bb = b / an - floor(b / an),
           cc = c / an - floor(c / an);
    if ((fabs(aa) < eps || fabs(1 - aa) < eps) &&
        (fabs(bb) < eps || fabs(1 - bb) < eps) &&
        (fabs(cc) < eps || fabs(1 - cc) < eps))
      return an;
  }
  return -1;
}
int main() {
  scanf("%lf%lf%lf%lf%lf%lf", &a[0][0], &a[0][1], &a[1][0], &a[1][1], &a[2][0],
        &a[2][1]);
  l[0] = dis(0, 1), l[1] = dis(1, 2), l[2] = dis(0, 2);
  sort(l, l + 3);
  r = (l[0] * l[1] * l[2]) / (4 * S(l[0], l[1], l[2]));
  ag[0] = 2 * (pi / 2 - acos(l[0] / 2 / r)),
  ag[1] = 2 * (pi / 2 - acos(l[1] / 2 / r)), ag[2] = 2 * pi - ag[0] - ag[1];
  sort(ag, ag + 3);
  d = gcd(ag[0], ag[1], ag[2]), n = round((ag[0] + ag[1] + ag[2]) / d);
  printf("%.8lf\n", S(r * sin(d / 2) * 2, r, r) * n);
  return 0;
}
