#include <iostream>
#include <cmath>
using namespace std;
double rast(int x1, int y1, int x2, int y2){
	return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
int main() {
	double x1, y1, x2, y2, x3, y3,a,b,c,p=0;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	a = rast(x1, y1, x2, y2);
	b = rast(x2, y2, x3, y3);
	c = rast(x1, y1, x3, y3);
	p = (a + b + c) / 2;
	cout << sqrt(p*(p - a)*(p - b)*(p - c));
}