#include<bits/stdc++.h>
using namespace std;
int x1,z1,x2,z2,x3,z3;
double jv(int x,int xa,int y,int ya)
{
	return 1.0*sqrt(abs(xa-x)*abs(xa-x)+abs(ya-y)*abs(ya-y));
}
int main()
{
	cin>>x1>>z1>>x2>>z2>>x3>>z3;
	double a=jv(x1,z1,x2,z2);
	double b=jv(x2,z2,x3,z3);
	double c=jv(x1,z1,x3,z3);
	double p=(a+b+c)/2;
	double s=sqrt(p*(p-a)*(p-b)*(p-c));
	printf("%.2f",s);
	return 0;
}