#include <stdio.h>
#include <math.h>
int main()
{//用float设x，结果会有零点几的误差
	double x1,x2,x3,y1,y2,y3,a=0,b=0,c=0,sum=0,i=0;
	scanf("%lf %lf %lf %lf %lf %lf",
	&x1,&y1,&x2,&y2,&x3,&y3);
	a=sqrt(pow(x2-x1,2)+pow(y2-y1,2));
	b=sqrt(pow(x3-x1,2)+pow(y3-y1,2));
    c=sqrt(pow(x2-x3,2)+pow(y2-y3,2));
    i=(a+b+c)/2.0;
	sum=sqrt(i*(i-a)*(i-b)*(i-c));
	printf("%.2f",sum);
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
double a1,b1,a2,b2,a3,b3;
double get_ans(double x1,double y1,double x2,double y2)
{
	double ans=sqrt((pow((x1-x2),2)+pow((y1-y2),2)));
	return ans;
}
int main()
{
	cin>>a1>>b1>>a2>>b2>>a3>>b3;
	double temp1=get_ans(a1,b1,a2,b2);
	double temp2=get_ans(a1,b1,a3,b3);
	double temp3=get_ans(a2,b2,a3,b3);
	double halfc=(temp1+temp2+temp3)/2;
	double ans=sqrt(halfc*(halfc-temp1)*(halfc-temp2)*(halfc-temp3));
	printf("%.2f",ans);
}