#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
int main(){
	double x1,y1,x2,y2,x3,y3,ab,ac,bc,p,s;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	ab = sqrt(pow(x1-x2,2)+pow(y1-y2,2));
	ac = sqrt(pow(x1-x3,2)+pow(y1-y3,2));
	bc = sqrt(pow(x2-x3,2)+pow(y2-y3,2));
	p = (ab+ac+bc)*1.0/2;
	s = sqrt(p*(p-ab)*(p-bc)*(p-ac));
	printf("%.2lf",s);
	return 0;
}