#include<bits/stdc++.h>
#define int long long
using namespace std;
double x1,y1,x2,y2,x3,y3,x,y,z,p;
signed main()
{
	cin>>x1>>y1>>x2>>y2>>x3>>y3;
	x=sqrt((x2-y1)*(x2-y1)+(y2-y1)*(y2-y1));
	y=sqrt((x3-x1)*(x3-x1)+(y3-y1)*(y3-y1));
	z=sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
	p=(x+y+z)/2;
	printf("%.2lf",sqrt(p*(p-x)*(p-y)*(p-z)));
	return 0;
}