#include <bits/stdc++.h>
int main() {
  const double eps = 1e-6;
  double x[3], y[3];
  for (int i = 0; i < 3; ++i) scanf("%lf%lf", &x[i], &y[i]);
  x[1] -= x[0];
  x[2] -= x[0];
  y[1] -= y[0];
  y[2] -= y[0];
  x[0] = y[0] = 0;
  double cx = (y[2] * (x[1] * x[1] + y[1] * y[1]) -
               y[1] * (x[2] * x[2] + y[2] * y[2])) /
              (x[1] * y[2] - x[2] * y[1]) / 2;
  double cy = (x[2] * (x[1] * x[1] + y[1] * y[1]) -
               x[1] * (x[2] * x[2] + y[2] * y[2])) /
              (x[2] * y[1] - x[1] * y[2]) / 2;
  double dx[3], dy[3];
  for (int i = 0; i < 3; ++i) dx[i] = x[i] - cx, dy[i] = y[i] - cy;
  double sin_t1 =
      (dx[0] * dy[1] - dx[1] * dy[0]) / (dx[0] * dx[0] + dy[0] * dy[0]);
  double cos_t1 =
      (dx[0] * dx[1] + dy[0] * dy[1]) / (dx[0] * dx[0] + dy[0] * dy[0]);
  double sin_t2 =
      (dx[0] * dy[2] - dx[2] * dy[0]) / (dx[0] * dx[0] + dy[0] * dy[0]);
  double cos_t2 =
      (dx[0] * dx[2] + dy[0] * dy[2]) / (dx[0] * dx[0] + dy[0] * dy[0]);
  for (int n = 3; n <= 100; ++n) {
    for (int i = 1; i < n; ++i) {
      if (fabs(sin_t1 - sin(2 * M_PI / n * i)) > eps ||
          fabs(cos_t1 - cos(2 * M_PI / n * i)) > eps)
        continue;
      for (int j = 1; j < n; ++j) {
        if (fabs(sin_t2 - sin(2 * M_PI / n * j)) > eps ||
            fabs(cos_t2 - cos(2 * M_PI / n * j)) > eps)
          continue;
        printf("%.9f\n",
               (dx[0] * dx[0] + dy[0] * dy[0]) * sin(2 * M_PI / n) * n / 2);
        return 0;
      }
    }
  }
  return 0;
}
