#include<bits/stdc++.h>
using namespace std;
int main()
{
	double x1,y1,x2,y2,x3,y3;
	cin>>x1>>y1>>x2>>y2>>x3>>y3;
	double a=sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
	double b=sqrt((x3-x1)*(x3-x1)+(y3-y1)*(y3-y1));
	double c=sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
	double p=(a+b+c)/2.0;
	double s=sqrt(p*(p-a)*(p-b)*(p-c));
	cout<<fixed<<setprecision(2)<<s;
	return 0;
}