#include <bits/stdc++.h>
double xa, ya, xb, yb, xc, yc;
double a, b, c, A, B, C, x, y;
double length(double x, double y) { return x * x + y * y; }
double gcd(double a, double b) {
  return fabs(b) < 1E-4 ? a : gcd(b, fmod(a, b));
}
int main() {
  scanf("%lf%lf%lf%lf%lf%lf", &xa, &ya, &xb, &yb, &xc, &yc);
  y = length(xc, yc);
  a = xa - xc, b = ya - yc, c = (length(xa, ya) - y) * 0.5;
  A = xb - xc, B = yb - yc, C = (length(xb, yb) - y) * 0.5;
  y = 1 / (a * B - A * b);
  x = (c * B - C * b) * y, y *= a * C - A * c;
  a = atan2(xa -= x, ya -= y);
  b = atan2(xb -= x, yb -= y);
  c = atan2(xc -= x, yc -= y);
  a = gcd(gcd(fabs(b - a), fabs(c - a)), 2 * M_PI);
  printf("%.8lf", length(xa, ya) * sin(a) * M_PI / a);
  return 0;
}
