#include<bits/stdc++.h>
using namespace std;

int main()
{
	double x1,y1,x2,y2,x3,y3;
	cin>>x1>>y1>>x2>>y2>>x3>>y3;
	double s=0.5*abs((x2-x1)*(y3-y1)-(x3-x1)*(y2-y1));
	cout<<fixed<<setprecision(2)<<s;
	return 0;
}