#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0), eps = 1e-4;
double fgcd(double a, double b) {
  return fabs(a) < eps ? b : (fabs(b) < eps ? a : fgcd(b, fmod(a, b)));
}
int main() {
  double a, b, c, d, e, f;
  cin >> a >> b >> c >> d >> e >> f;
  c -= a;
  e -= a;
  d -= b;
  f -= b;
  a = (c * c + d * d) / 2;
  b = (e * e + f * f) / 2;
  double ov = 1.0 / (d * e - c * f);
  double A = (d * b - f * a) * ov, B = (e * a - c * b) * ov;
  double R = sqrt(A * A + B * B), G1 = asin(sqrt(a * 2) / (R * 2)),
         G2 = asin(sqrt(b * 2) / (R * 2)),
         G = asin(hypot(c - e, d - f) / (R * 2));
  G = fgcd(G1, fgcd(G2, pi));
  G = pi / round(pi / G);
  A = round(pi / G) * R * R * sin(G * 2) / 2;
  printf("%.8lf\n", A);
}
