#include <bits/stdc++.h>
using namespace std;
double alpha[3], r, s, a[3];
double PI = 3.1415926535897932384626433832795;
pair<double, double> v[4];
int main() {
  for (int i = 0; i < (3); ++i) cin >> v[i].first >> v[i].second;
  v[3] = v[0];
  for (int i = 0; i < (3); ++i)
    a[i] =
        sqrt((v[i + 1].first - v[i].first) * (v[i + 1].first - v[i].first) +
             (v[i + 1].second - v[i].second) * (v[i + 1].second - v[i].second));
  for (int i = 0; i < (3); ++i) {
    for (int j = 0; j < (3); ++j)
      if (i != j)
        alpha[i] += a[j] * a[j];
      else
        alpha[i] -= a[j] * a[j];
    alpha[i] /= 2;
    for (int j = 0; j < (3); ++j)
      if (i != j) alpha[i] /= a[j];
    alpha[i] = acos(alpha[i]);
  }
  for (int n = (3); n <= (100); ++n) {
    bool p = true;
    for (int i = 0; i < (3); ++i)
      if (fabs(sin(alpha[i] * n)) > 1e-5) {
        p = false;
        break;
      }
    if (p) {
      r = a[0] / sin(alpha[0]);
      r /= 2;
      s = n * r * r * sin(2 * PI / n) / 2;
      printf("%.6lf", s);
      return 0;
    }
  }
  return 0;
}
