#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;

int main() {
	double x1, y1, x2, y2, x3, y3, a, b, c, p, s;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	a = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
	b = sqrt((x1 - x2) * (x1 - x2) + (y1 - y3) * (y1 - y3));
	c = sqrt((x1 - x3) * (x1 - x3) + (y2 - y3) * (y2 - y3));
	p = (a + b + c) / 2.0;
	s = sqrt(p * (p - a) * (p - b) * (p - c));
	printf("%.2lf", s);
	return 0;
}