include

include

include

using namespace std; int main(){

double a1,a2;
double b1,b2;
double c1,c2;
cin>>a1>>a2>>b1>>b2>>c1>>c2;
double ab=sqrt((a1-b1)*(a1-b1)+(a2-b2)*(a2-b2));
double ac=sqrt((a1-c1)*(a1-c1)+(a2-c2)*(a2-c2));
double cb=sqrt((b1-c1)*(b1-c1)+(b2-c2)*(b2-c2));
double c=(ac+ab+cb)/2;
double s=sqrt(c*(c-ab)*(c-cb)*(c-ac));
printf("%.2lf",s);
return 0;

}