include

include

include

using namespace std; int main(){

double x1,y1,x2,y2,x3,y3;
cin>>x1>>y1>>x2>>y2>>x3>>y3;
double a=sqrt(pow(x2-x1,2)+pow(y2-y1,2));
double b=sqrt(pow(x3-x2,2)+pow(y3-y2,2));
double c=sqrt(pow(x3-x1,2)+pow(y3-y1,2));
double p=(a+b+c)/2;
double s=sqrt(p*(p-a)*(p-b)*(p-c));
printf("%.2lf",s);
return 0;

}