#include <bits/stdc++.h>
using namespace std;
const double EPS = 1e-2;
const double Pi = acos(-1);
double X1, Y1, X2, Y2, X3, Y3, P, A, B, C, S, R, Angle1, Angle2, Angle3, T,
    X[4], Y[4];
double Dist(double XX1, double YY1, double XX2, double YY2) {
  return sqrt((XX1 - XX2) * (XX1 - XX2) + (YY1 - YY2) * (YY1 - YY2));
}
double FMod(double X, double Y) { return X - (int)(X / Y) * Y; }
double FGCD(double X, double Y) {
  if (fabs(Y) < EPS) return X;
  if (fabs(X) < EPS) return Y;
  return FGCD(Y, FMod(X, Y));
}
int main() {
  scanf("%lf%lf", &X[1], &Y[1]);
  scanf("%lf%lf", &X[2], &Y[2]);
  scanf("%lf%lf", &X[3], &Y[3]);
  A = Dist(X[1], Y[1], X[2], Y[2]);
  B = Dist(X[2], Y[2], X[3], Y[3]);
  C = Dist(X[3], Y[3], X[1], Y[1]);
  P = (A + B + C) / 2;
  S = sqrt(P * (P - A) * (P - B) * (P - C));
  R = A * B * C / 4 / S;
  Angle1 = acos(1 - A * A / 2 / R / R);
  Angle2 = acos(1 - B * B / 2 / R / R);
  Angle3 = 2 * Pi - Angle1 - Angle2;
  T = FGCD(FGCD(Angle1, Angle2), Angle3);
  printf("%.6lf", Pi * R * R * sin(T) / T);
  return 0;
}
