#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
	const int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};
	int x[3], y[3];
	for (int i = 0; i < 3; ++i) cin >> x[i] >> y[i];
	double ans = 0;
	auto dfs = [&](auto f, int id) -> void
	{
		if (id >= 3)
		{
			int vx[2], vy[2];
			for (int i = 1; i < 3; ++i)
			{
				vx[i - 1] = x[i] - x[0];
				vy[i - 1] = y[i] - y[0];
			}
			double tmp = abs(vx[1] * vy[0] - vx[0] * vy[1]) / 2.0;
			ans = max(ans, tmp);
			return;
		}
		for (int i = 0; i < 4; ++i)
		{
			x[id] += dx[i];
			y[id] += dy[i];
			f(f, id + 1);
			x[id] -= dx[i];
			y[id] -= dy[i];
		}
	};
	dfs(dfs, 0);
	printf("%.1f\n", ans);
}