#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
int main(){
	double x1,x2,x3,y1,y2,y3;
	cin>>x1>>y1>>x2>>y2>>x3>>y3;
	double a=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
	double b=sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));
	double c=sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
	double p=(a+b+c)/2;
	double s=sqrt(p*(p-a)*(p-b)*(p-c));
	cout<<fixed<<setprecision(2)<<s;
	return 0;
}