poj_2242

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
#include <cstdlib>
using namespace std;
#define clc(s,t) memset(s,t,sizeof(s))
#define PI 3.141592653589793
double dis(double a,double b,double c,double d){
return sqrt((c-a)*(c-a)+(d-b)*(d-b));
}
int main(){
double a,b,c,d,e,f;
while(scanf("%lf %lf %lf %lf %lf %lf",&a,&b,&c,&d,&e,&f)!=EOF){
double s = fabs(a*d+b*e+c*f-d*e-a*f-b*c);
printf("%.2f\n",PI*dis(a,b,c,d)*dis(a,b,e,f)*dis(c,d,e,f)/s);
}
return 0;
}