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