#include <bits/stdc++.h>

using namespace std;

int main()
{

	double x1, y1, x2, y2, x3, y3, a1, a2, a3, p, S;
    
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    
	a1 = sqrt((x1 - y1) * (x1 - y1) + (x2 - y2) * (x2 - y2));
    
	a2 = sqrt((x1 - y1) * (x1 - y1) + (x3 - y3) * (x3 - y3));
    
	a3 = sqrt((x3 - y3) * (x3 - y3) + (x2 - y2) * (x2 - y2));
    
	p = (a1 + a2 + a3) / 2;
    
	S = sqrt(p * (p - a1) * (p - a2) * (p - a3));
    
	cout << fixed << setprecision(2) << S << endl; 
    
	return 0;
}