#include <iostream>

 #include <cstring>

 #include <cstdlib>

 #include <cstdio>

 #include <numeric>

 #include <cctype>

 #include <cmath>

 #include <algorithm>

 #define PI acos(-1)

 using namespace std;

 double calc_dis (double x1, double y1, double x2, double y2) {

     return sqrt ((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));

 }

 int main () {

     ios :: sync_with_stdio(false);

     double x[], y[];

     while (cin >> x[] >> y[]) {

         for (int i = ; i < ; ++ i) {

             cin >> x[i] >> y[i];

         }

         double a, b, c;

         a = calc_dis (x[], y[], x[], y[]);

         b = calc_dis (x[], y[], x[], y[]);

         c = calc_dis (x[], y[], x[], y[]);

         //cout << a << " " << b << " " << c << endl;

         double p = (a + b + c) / ;

         double s = sqrt (p * (p - a) * (p - b) * (p - c));

         //cout << "s : " << s << endl;

         double d = a * b * c / ( * s);

         printf ("%.2f\n", PI * d);

     }

     return ;

 }