#include <iostream>
#include <cmath>
using namespace std;
#define maxn 1024
const int N = 1e6 + 100;

int dis(int x1, int y1, int x2, int y2) {
	return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}

int P(int a, int b, int c) {
	return (a + b + c) / 2;
}

int Square(int p, int a, int b, int c) {
	return sqrt(p * (p - a) * (p - b) * (p - c)); //Helen-QinJiu zhao formula
}

int main() {
	int x1, y1, x2, y2, x3, y3;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	int a = dis(x1, y1, x2, y2);
	int b = dis(x1, y1, x3, y3);
	int c = dis(x2, y2, x3, y3);
	int p = P(a, b, c);
	printf("%.2lf", (double)Square(p, a, b, c));
	return 0;
}