#include <iostream>
#include <cmath>
using namespace std;
//функция высчитывает расстояние между двумя координатами, координаты передаются в функцию при вызове
double side(double ax,double bx,double ay,double by,double az,double bz){
	return sqrt((bx-ax)*(bx-ax)+(by-ay)*(by-ay)+(bz-az)*(bz-az));
}
int main() {
	double ax,ay,az,bx,by,bz,cx,cy,cz;
	cin>>ax>>ay>>az>>bx>>by>>bz>>cx>>cy>>cz;
	double a=side(bx,ax,by,ay,bz,az);
	double b=side(cx,ax,cy,ay,cz,az);
	double c=side(bx,cx,by,cy,bz,cz);
	double p=(a+b+c)/2;
	double s=sqrt(p*(p-a)*(p-b)*(p-c));
	cout<<s;
	return 0;
}

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LTYgLTIuMyAtOC4yIDEuOSAtNy44IDAuMiAtOC41IDMuNCAtOC45

-6 -2.3 -8.2 1.9 -7.8 0.2 -8.5 3.4 -8.9