#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define rep(i, n) for(int i = 0; i < n; i++)

int main() {
	vector<double> x(3), y(3);
	rep(i, 3) cin >> x[i] >> y[i];
	int c = 4 * 4 * 4;
	double ans = 0;
	rep(i, c) {
		vector<double> tx = x;
		vector<double> ty = y;
		int ii = i;
		rep(j, 3) {
			int m = ii % 4;
			ii /= 4;
			if(m == 0) tx[j]++;
			if(m == 1) tx[j]--;
			if(m == 2) ty[j]++;
			if(m == 3) ty[j]--;
			double vx1 = tx[0] - tx[2];
			double vy1 = ty[0] - ty[2];
			double vx2 = tx[1] - tx[2];
			double vy2 = ty[1] - ty[2];
			double s = abs(vx1 * vy2 - vx2 * vy1) / 2;
			ans = max(ans, s);
		}
	}
	cout << fixed << setprecision(1) << ans << endl;
}