#include<bits/stdc++.h>
using namespace std;
double x1,y_1,x2,y2,x3,y3,a,b,c,p,s;
int main()
{
	cin>>x1>>y_1>>x2>>y2>>x3>>y3;
	a=sqrt(pow(abs(x1-y_1),2)+pow(abs(x1-y_1),2));
	b=sqrt(pow(abs(x2-y2),2)+pow(abs(x2-y2),2));
	c=sqrt(pow(abs(x2-y2),2)+pow(abs(x2-y2),2));
	p=(a+b+c)/2;
	s=sqrt(p*(p-a)*(p-b)*(p-c));
	printf("%.2lf",s);
	return 0;
}